Even if there is water damage, you have a one-up on those rebuilding pull campers. The framing is all steel, except for the very front of the cab-over bunk. That means very little to tear apart and rebuild. It does look like you had some water damage up there though. Tear off the paneling in the bunk and take a look at the wood. If it looks fine, then all you have to do is seal the seams on the outside. If the wood is bad, then you get to tear it apart from the outside. The fun part of course is attaching new interior paneling to that steel frame. The process isn't too hard if you know the basics. I rebuilt our bunk over 3-4 weekends, which included a lot of down-time going to pick up supplies.
1992 Dutchmen 30FK
2 adults who don't know they are adults, 3 furry feline children