Thanks for the posts guys. So this weekend I replaced the floor with the help of a good friend, whom I owe a huge debt of gratitude to, and my brother-in-law, who I will always be indebted to for one reason or another.
We removed the bed from the back and pulled up the carpeting and linoleum and the plywood, joists (2x3 wood joists), and insulation all came with it. Needless to say, I had quite the "oh jesus" moment. We inspected everything and there was no mold anywhere....phew! $100 in lumber and screws later we had a solid floor. The bed went back pretty quickly and we used carpet tiles for the floor.
Total cost of project:
2.5 sheets of plywood= $63
9 - 2x3x8'= $15
2 - 2x4x10'=$8
2 - box of screws~$12
2 - boxes of carpet tiles=$180
1 - case of beer=$22 (Sam Adams)
$300 on the nose
Overall, it was a pain in the ass and took longer than I wanted it too.
But it beats shelling out $12K or more for a new, or at least new to me trailer.
The bottom line: though it seemed daunting at first, especially when we realized how far gone the floor was, it really wasn't a tough job to do.
To follow on with mazak's comment, last year we had sealed the entire trailer; windows, doors, roof seams, etc. I'm going to double check for cracks, which I found already on the skylights, and for any gaps we missed. We should be good by the end of next weekend.