We just did our roof and hit a lot of damage in the walls and floor. It took a lot of hard work, but the materials for the roof including all new EPDM, sheathing, rafters, etc. was well under $1000. We spent more that on the total project, but we also upgraded/remodeled while we were at it. I'm handy, but certainly no carpenter, so it's a very doable project. I would start by peeling away the ceiling to see what damage you can see by removing the obviously damaged panels. My guess is you'll eventually get into the walls and maybe the roof.
