Just keep gutting. You'll end up pulling all the stuff, anyway to fix the floor.
Plan on replacing the rotted frame pieces with new stuff. The few ceiling joists I had that were rotten were fixed by ledgering on new tails to the bottom chord of the truss and fastening to the wall top plate. You can find a picture in the Cowboy/Hilton thread in my signature line.
A project like this seems too big and costly at the start. Just take it at a moderate pace, fixing certain areas at a time. Don't get discouraged at the "big picture". If money is tight, look around for pieces you can get free or at a bargain. I tried to keep a steady pace because I was certain that if I stopped in mid-restoration, the whole thing might not get done. You're the boss so set your time accordingly.
We'll be here for 'ya with advice and encouragement. The really cool thing is that you get to rebuild the trailer to your needs and if you do a good job, it will be a better rig when you're done than when it left the factory. I have no regrets.
