If you just want to replace the top flooring instead of the base (whole thing), I have done a few repairs to my 34 foot 1986 Limited and one of the easiest and good looking was to replace the carpet in the living room section with stick on tiles. I did the same in the bath. In the LR I put down 1/4 inch plywood over the pressed board flooring to help the tile stick and it worked great. In the bath I just stuck it on the pressed board and it is still doing OK.
Inexpensive, much easier to clean, and those stick on tiles look so good I've had people ask me if it was ceramic. And with a good large sissors and tape measure it's relatively easy to do. Eventually I will do the whole trailer with them but being full time, it's hard to find the place or time.
If you are trying to do the whole floor down to the steel, I believe it would be better to take off the shell, because when I replaced a small section of the subfloor, it looked like if I had been forced to do more, it would have been important for it to be attached to the shell. Others can give you better input on that. But, if the subfloor is in reasonably good shape (not soft), the tile works great.
Full Time.....keeping the shiny side up