First thing you need to do is take it to a competent RV repair facility that can do a 'Blower Door Test', or in the case of an RV, an authorized Seal Tite Systems franchised dealer and have them perform the test and isolate (and mark) where the outside seals are failed (why it's leaking). Once you do that, you need to ascertain how bad the water intrusion is, how much under the wallboard rot there is, if there is a mold issue (most likely) and remediation cost and if the cost is worth it or nor. It's not cheap by a long shot and the unit may not be worth the cost of repair.
Seal and caulk continuing maintenance is the most important thing concerning RV ownership, seals and caulk must be inspected every 6 months or what happens is what you have... water intrusion and most likely rotting structure, soaked insulation, mold growth and a serious issue.
