Welcome to the forums!
I don't see any pictures yet, so let me offer some general advice on how to do things as cheap as possible. What is your budget for the rennovation?
1) Do as much of your own labor as you possibly can. None of this is rocket science, so there is no sense in paying an RV tech $100/hr to do things for you.
2) Do as little as possible. If you can fix your floor rot issue by patching the floor rather than completely replacing the floor, then that is the cheap way to go.
3) Avoid scope creep. Avoid ever saying "as long as I am here, I might as well do..."
4) Use as much of the original interior as possible.
5) Manage your expectations... These projects tend to take a lot of time (years), and can get very expensive, depending on the scope of the rennovation. The advice I usually give buyers of vintage trailers is that they are really only buying a shell--everything else ends up being replaced.