Because the cab and coach sections of Class C's flex differently with their frame mountings in relation to each other, leaks in the over head section are all too common. Because it is attached to both.
Several older posts , with pictures, from members doing similar repairs.
I'll track them down and tell you how to find them.
At the top of the posts list in the Class C forums, right hand corner of the blue bar; click search this forum. Drop box will open.
Overhead Sleeper Rotted , and click search, responders have posted pictures of their fixes.
Also do the same for.
Mini Bunk Rebuild
& Bunk water Damage Rebuild
Good luck with your repairs and safe travels once you get moving.