EMD_Driver has pulled ceiling panels down and even on a 2004 model camper. He can give better explanation on what you will be up agasint.
Getting the panel down is one thing, being able to save it in the process may be another thing.
Since you smell the musty's, the water has been festering for some time. And it sounds like it may be up front. Was it the top front seam along the roof line?
A heads up, unless you have a full walk on roof, then you have the heavy corrugate board called Bub board under the rubber membrane and over the top of the rafters. That corrugate board can wick water and being a fiber material may be shot if it was wet. I hope this is not the case in your situation but it will be a choice you will be faced with if you find the bud bard wet.
You may be able to rent an inspection camera system. They are called bore scopes and have a light and camera in the end of a long flexible shaft. If you can find one, then use that up in the speaker hole and look around. You may find you have to come through the roof.
Good luck and hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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