Leaving the electric to someone else but have a few question

Keri..Yes, you CAN put a new breaker box in that space.( But perhaps it may not be the best location) I would advise that you should put it where it is both out of the way and accessable. Imagine a dark night and a breaker pops and needs to be reset. Having the box where it can be easily accessed is just a good practice.
Now then, just for peace of mind, you should replace the old wire with new material, and while doing so you can configure your new system to any particular needs you may have. You can hire an electrician to do the work, and tell him or her what your needs are for your system. Will you be boondocking a lot, or staying at RV parks with 30 amp service?? What kind of appliances and power load will you need? We are restoring a 19 foot Deluxe, and have decided to go with an all AC system, except for battery LED overhead and closet lights, since we have generator capacity for all the appliances and receptacles, and it saves the weight, expense and venting battery issues of installing a 12VDC seperate system.
Sorry for the verbose response, but the short answer is figure out your elec. requirements and hire an electrician who will install your new system. You will KNOW that your camper is protected by a safe system.

I'm not the expert. But I believe there is a difference between trailers and houses in the way that AC grounds are connected (something about hooking the ground and neutral together in a house breaker box but not in a camper, IIRC). There's nothing that a "regular" electrician would find difficult, but he must know the difference to prevent your getting shocked. I'd ask Vik.