Doesn't sound that bad to me. I've fixed a lot worse, how about half the floor of the TT and the entire rear corner? No biggy, love doing it. There is something also called CPES epoxy that hardens and restores wood.
Just bought a Trail Cruiser that had blowouts on both sides. One side took out the aluminum framing behind the wheel and bent up the steel wheel well and got up into the area behind the kitchen sink. So the last owner left the wheel well all bent up, patched it with an unsealed piece of aluminum and cramed towels up under the cabinet either to keep the water out or for insulation. Then covered the damage behind the wheel well with old plywood without any caulking. So I had to remove the galvanized wheel well and pound it back to straight, insulated the area and repaired the whole area behind the wheel all the way to the back with aluminum sheeting that is sealed in place, after drying out the area and sealing the wood with CPES. Unfortunately the floor behind the wheels has sagged an inch or so, but the wall and top don't seem to have sagged too, is weird, not sure why. I welded up an outrigger brace to keep the sag from going any further. The Cruiser has an aluminum frame and is built of a fiberglass, plywood, 1 1/2" white solid insulation and interior plywood sandwich, so leaks don't act the same as regular trailers where the water follows the wood frame, all leaks stay isolated in the same area, there are no water marks inside.
So, don't be afraid to attack the damage, I always look at these things as a challenge and love solving it. It might actually be less bad than you think.