I had the same thing happen on a 2010 Fuzion 383. I replaced the floor with the slide in place. It's not really that bad since the slide is relatively small.
In my case, the leak was caused by the caulking on the outside of the slide at the mid-seam was not done properly. This caused the caulk not to adhere to the slide wall and water ran down the lower part of the outside wall and wicked into the floor. Eventually the wood, well the pressed wood stuff, just disintegrated and the bolts pulled out.
Not a horrible job and if you're fairly handy with hand tools you can do it yourself. Probably save yourself a grand or so.