Welcome to the Forum.
Obviously this isn’t going to be a quick fix. IMO, you’re gonna want a garage to do the work inside so you you’re not worrying about additional water damage, vandalism etc while you’re doing the work.
I see several options:
1) You slowly tear the slide down, taking pictures and measurements while you slowly pull everything apart. Then using those measurements rebuild everything to specs.
2) You remove the slide completely, then instead of rebuilding it you basically put in a solid wall...no slide.
3) Sell the camper for parts and move on...
EDIT: wow just noticed the date..
The sheep always complain about the Sheepdogs UNTIL the Wolves show up then they beg for help!