Your renovations should be done in the following order to avoid having to do things twice:
1) Seal the trailer - any water that enters will damage whats there now, creating more work later, and will damage any work you do in the future. Sealing is an ongoing process, i try to check my seals, seams and the inside for leaks quarterly.
2) Axels and brakes - unless you are towing only very short distances you need to have good axels or you will be damaging the trailer. I would hate to build new cabinets for my trailer then shake them apart because of bad axels. If you are moving the trailer at all you need brakes and lights for safety.
3) Floor/Frame - like the foundation of a house this is the foundation of the trailer, if you build a cabinet on a bad floor you just have to pull it out later to fix the floor.
4) Major systems, Plumbing, electircal and appliances. I found it easiest to do this all at once since I had to remove the beds and part of a cabinet to run plumbing and electrical wire. this was also a good time to install new floor covering since I had furniture removed.
5) Decor/polishing - again, no point in making it pretty if you can't tow it or keep the interrior dry.
If the floor is solid and the axels useable you can always use the trailer as an aluminum tent until you get the plumbing fixed (we camped with no plumbing when the water pump quit and used a bucket to flush the toilet, and had some non working interrior lights for a while)
1977 Safari Land Yacht
2005 Toyota Tundra SR5
2010 Ford Flex Ecoboost