The typical RV is built from the bottom and and inside out. That is the floor is put on the frame, usually to "finish" that is the sheet-roll flooring is even put down at this stage.
Next the base cabinetry is installed, sometimes the wall cabinets are brought in even before the walls are framed.
Often the shower, refer and other large items are brought in, before the walls are framed. This is because the door will be too small to allow those items to easily be installed.
Then the walls are framed up and the inside finish work is continued.
For a complete floor replacement, the cabinetry, walls (roof), appliances, etc all need to be removed.
Basically you are starting over from a bare frame.
I've done RV rebuilds, I would walk away from something this complex and look to sell the piece parts for what I could.
