Do a search for my username in Repair for "floor replacement". I, too, installed a welded 2x2 frame beneath. Hopefully your problem is not that extensive and/or you have a joist floor.
If you have floor vents, you have a joist floor, and should be able to just cut out the bad areas, and replace. If all of your vents come out the sides of seats and cabinets, then you have a laminate floor like mine. Impossible to do a spot repair, as you have to go all the way to the walls before you get to anything solid. Must be a wall-to-wall repair. Much time, much patience, much planning. Dealers won't even quote the job.
Ultra-lite structural-laminate floors (2 pieces of ¼" plywood laminated on each side of 1½" dense Styrofoam), are not intended by the manufacturers to be repairable.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller