Well your Tiffin is several steps above my Bounder so take it for what it's worth.
I had a very small leak under my Splendiee Combo. I kept thinking some underwear in the drawer below wasn't getting dry. Finally got to tracking it down and I found the fitting on the P-trap had a flaw in it.
To pull the washer I had to remove the back wall of the cabinet above as Fleetwood didn't put access to the stop valves. (Not surprised as they covered the valve for the ice maker too.)
Once I got that done I built a table on a moving dolly I have making it the height the same as the cabinet floor. Pulled the combo out and was able to wheel it out of the way. Rebuilt the drain pipe, and secured it from flopping around. Seven plus feet horizontal pipe plus the stand pipe just flopping around.
Got pinched for time so I still need to put in an access panel to get to the valves but at least I have no leak.