The only real solution is fix the leaks, tear out ALL rotted, soft wood and replace. No magic tricks, just start removing and dismantling until you don't find water damage. If any rotted wood is left, upon repair the rot will spread to the new wood. Also, be aware of possible mold in wet areas. That can be a health hazard as you work and definitely if you inhabit the contaminated trailer.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI