I'm very, very new, in fact, I'm a moron when it comes to camping, campers, etc. I've been camping many times with friends and love it, but never have owned one. My friend has offered me her camper ...
1. It's probably more than you want to spend to fix it right. 2.The floor is soft because the camper leaked.
So, find and fix any and all leak(s) and put 5/8 or 3/4 inch plywood over the entire floor and use the camper as is. If you don't fix the leak(s), you won't be using it long.