Find the source of the original problems and repair it. If it is a leaky roof remove the old sealant using a putty or utility knife. Using a caulking gun filled with sealant apply the new sealant over the area that is leaking. With a moist finger or disposable spoon flatten the sealant.
Remove the trim holding down the flooring with a pry bar. Pull up the flooring and save the flooring for a pattern.
Pull off any water-damaged wallpaper or paneling. If removing paneling save for pattern matching. If insulation behind the paneling is not destroyed leave it, but if it is, replace it with new insulation.
Spray bleach solution over the sub-flooring and where bad paneling has to be replaced. This will prevent mold and mildew. Let it thoroughly dry.
Copy the edges of the old paneling as a pattern for new paneling. Glue the new panel to the frame of the RV. Do the same with the flooring.
Lay flooring and replace molding by attaching it with new nails. Lastly, install new wallpaper.
