The first thing necessary is to find out exactly where the water intrusion is coming from. Some things I would suggest that you check initially would be:
1.) Check the water piping and fittings and drain lines and fittings under the galley sink for loose or broken piping, fittings, etc.
2.) Check the refrigerator
drain tube in the back of the fridge
. In order to see it, you'll need to remove the outside lower vent louver in the area behind the fridge
. It is a common problem with older fridges in that the condensation drain hoses rot off over the years, and this could possibly be a source for wetness in that area.
3.) Check the integrity of the outside fridge
vents and make sure that they aren't cracked or broken. (You can do this while you're checking on the drain hose behind the fridge.)
4.) There is also another common problem, which is created by the slight slope of the upper half of the shell of the trailer, which is not actually vertical, which can and does often allow water to enter the trailer via the upper fridge vent outside. Some baffles to divert the water from running down the side into the vents can be fabricated to redirect the water from running inside the trailer. There are many threads on the forum which address dealing with that issue and preventing that from happening.
5.) Check the caulking sealant around your main entry door for cracks or separation. Also check the weatherstripping around the door as well, to make sure it hasn't become old, cracked and rotted too.
This isn't an all-inclusive list, but it should give you a few things to check on, if for no other reason other than to rule them out. Good luck with your project.