Where do I start with my Shasta Compact?

IT really depends on the extent of damage and what your set up is for doing the work.
The best way to go if you have the workspace is to go from the outside in....which basically is reverse the building process and then rebuild the way it was built. Taking the skins off...easy to do...especially just the sides will let you see immediately how much rot you are dealing with. If the sub floor is rotted you are gonna need to take the skins off anyway to do a proper reframing.

If you have the toaster shape vs canned ham the framing is pretty square and you can do it inside out. And if you don't have a workspace that allows you to take it down to the frame, then you just need to do the best you can.

I did mine as a partial skin off restore. Had I known then what I know now, I likely would have rebuilt from the frame up....it probably would have been easier. But I did have space constraints. If you just take off the side skins....make sure to use supports on the inside to keep it from cratering.

You can use ash which has a sort of silvery color, you can use regular plywood.. it just depends on what the finished look you want to achieve is. If you will be painting the interior, I'd go with plywood.

I'm doing an outside in and down to the frame. All four corners leaked so soft floor ply was an issue, as were front and back windows and vent. I could have done an inside only and reached much of the rot, but windows still would have had to be removed to polish and reseal, and J rail, and eventually sub floor stringers that my Scotty walls attach to and because I only want to do this once I went ahead and peeled it all off. I'm fortunate that we have a Quanset style carport that is dry and outta the weather so until the snow falls I can keep going ( don't like frozen fingers). I regret loosing this summer for some quality beach camping but in the back of my mind I could see having to re-repair, since I would not have fixed the problems that caused the leaks in the first place with out skinoff.
I decided that I would look at this year as an experience of building a camper from scratch, with plans and lots of reusable parts, kind of like building model planes when I was a kid.
I gained the friendship of neighbors who I didn't really know until I dragged this project home, who now come over regularly to help, or snoop, or bring with them a chair and some beers, and get all nostalgic.
It might be unfair for me to tell someone else to go the route I chose because I restore things for a living and spending an unexpected amount of time doing it is not a surprise to me. An inside repair, enough to stabilize, and then a season of outings with campfires and starlit nights, and then some serious fix-its over the winter might make more sense to someone who doesn't love to just take things apart on a regular basis.
However you do it, keep the thought of campfires and coffee pots and starlit nights, as you muddle through what size screws you'll need or where you'll find a decent replacement sink.

WELCOME TO VTT siskiwit!!!

IMHO;
With the year and model you have, and the back ceiling pic you posted, you should take the roof skin off, throw away fiberglass insulation, and then remove hidden cross beams, marking where they were. Then start lying in new ceiling panels, fitting the "tuck in channeled" cross beams with the ceiling panel edges. Then drop in hidden cross beams. There will be small sticks on the sides to put in also. Then re-insulate, run wires if needed. Then put roof skin back on.
The side wall panels on that model can be replaced from inside if desired.
The ceiling panels should not be done from the inside on this year and model due to the ceiling going over the top of the wall panels.
The front and back walls should be done from out side skin removed due to those over lapping the side wall edges also.
1/3 structural strength comes from those panels over lapping the side wall edges.
Don't do too many areas at once or risk cave in!!

Also see this thread, 66 Compact, roof and ceiling are being replaced;
vintagetrailertalk.freeforums.net/thread/479/compact-bring-boil-reduce-simmer

Your wall panel where the breaker box is, in the closet, doesn't look that bad!

Good Luck and more importantly, Have Fun!
soup

I did mine with only opening the skin seams, including building a completely new subfloor, but it was because I had no inside space to work. would have been much easier if I could have stripped it.

Here's a thread from the old forum by Pathfinder3081 (dunno if he came over to the new forum or not) describing how to build an undercarriage to lower the trailer to get it into the garage using casters, although the pics are gone, so you'd need to find him, probably: vintageshasta.proboards.com/thread/5171?page=1

Thank you thank you THANK YOU for the welcome and all the first step suggestions! Pathfinder3081 was able to get me the pictures from the former forum, but we realized I have a different style underbody compared to his. Before I can even start the process of taking the damaged parts out I have to fit it in my garage and that has proven to be quite a challenge with a 7 foot vertical opening. Plan A was to deflate the tires and roll it. That idea failed when we realized it's REALLY heavy, wouldn't roll, was still too tall, and didn't want to take the chance of scuffing up the concrete in the garage or ruining the tires. Plan B was taking off the wheels and letting it sit on the U-bolts (the lowest point of the camper)and push it in. This ended up with the same results as plan A...toooooo heavy. Plan C was also a fail. We tried putting car jacks equipped to handle 3000 pounds each but they just wouldn't get low enough. We had positioned them under the tongue and one under the back where the weight was evenly distributed. We needed about an inch and a half to make it fit Now comes plan D! We are going to take it to a mechanic where they can put it on a lift and take off the 50 year old rusted bolts that hold the axel....as well as check out the bottom for cracks and weakness with an experienced eye. We're going to leave it to a professionals to get them off with the special tools and replace them with new. Then we will get her home and jack it up, take off the axel, and pull it inside on car jacks. Removing the axel will give us at least 6 inches of clearance and peace of mind the bottom is structurally okay. Yes it will cost us a bit of $$ but at least we won't have to rent a garage to store it and drive to it to work on. It will be nice to be able to work on it from where we live. We rent a townhouse so altering the garage door opening isn't an option. Right now the plan is to buy a couple more "movers dolly) from Harbor Freight with caster wheels (rated at 1000 lb capacity each) and put 6 or so underneath once it's inside to keep it well balanced and movable. We have plenty of vertical height once it's through the opening as well.

We are not fans of the ugly paneling on the walls and will not be replacing it with birch wood paneling(although I bet it would look pretty fantastic if we did!). I really want to paint inside and customizing it to be my own. Priority #1 will be making it water tight...no more leaks! After that it will be finding the materials that will work well together allowing "flex" when we take it on long distance trips.

Right now I name her the Jo Jo the Jaolopy because I'm so frustrated at making a home for her. With A LOT of time and elbow grease she will be a shining gem once again. And I'm sure we'll have a million more questions along the way.

Thank you again for all the help, suggestions, ideas, and comments. There certainly seems to be a feel of "family" among the openness and eagerness to help among vintage camper owners. I love it!

Jenny from Sconnie!

What type of thickness is good for lauan if used on the walls and ceiling, 1/8"? Is it easily bendable to match the curves in the ceiling? I live in Menards only territory (home town of Menards) and I see in their add this week they are selling it  1/8" for $10.49 for a 4x8 sheet (special order). I will do some price comparisons for Lowe's and Home Depot but I'd have to drive at least an hour to get to the closest one.

I've also seen so many variances in insulation use. Some use the bubble wrap kind and others use the pink thick sheets. How do you choose?