Leaks!!

My adventure started when we headed to san antonio the jayco was in storage and while there a field rat found its way in.... and died.... upon searching for his entrance i discovered the previous owner must have had a blow out which busted the wheel well which is plastic when that happened it also busted the backer board around it. while i was uncovering this to repair i noticed daylight shining through around the outside electrical outlet.... and the wall so soft you can out your finger through it. I'm concerned the flooring is also rotten out. is there a way to just fix the leak or is it possible its at a point where some major rework needs to be done? I would post photos but cant figure out how.