Here's a link to the floor replacement project I did on my slide out. Had the same symptoms, when I pulled the carpet I found that the factory used Reflectix insulation under the carpet and that was blocking the moisture from the leak from wicking up into the carpet, so the leak went undetected much longer than it should have.
I found that the Darco wrap (the black plastic tarp-like material) was letting water in but not out, so the wood framing on the slide and the edge of the main floor never dried out and just rotted away like a science project.
This may sound like a lot of work, but if the dealer opens up the project and finds what I found that $3k can go to $6k quickly....
