I would try a simple approach first, before trying to fit sheet paneling to the multiple complex curves of our molded type trailers.
If you have the teddybear fur type of interior "carpet", this is a type of marine spun polyethelene fiber. It is not backed, and is only press formed into flat form during manufacture. It will hold various forms of dirt and bacteria, but its' material composition will not normally allow for this debris to bond. I would first try cleaning the carpet by using a "Quat" based sanitizer mixed with water. You should be able to obtain this from any bar and restaurant supply house. Tell them you want a liquid third sink rinse "QUAT" based sanitizer. If this type of supply house is not available, a pool supply will have this sanitizer in a more concentrated form that they use in pool water treatment.
The label should list Quaterinary .........Chloride, as one of the first active ingredients on the label from either source.
You want a mixture of no more than one ounce per gallon of water for you application. I would take a garden type pump sprayer, mix my sanitizer with water, and spray all surface areas wet. Allow to set for approx 15 minutes. Then using a rental carpet extractor cleaner with the upholstery cleaning hand wand and suction hose, use the same sanitizer water mix and reapply to all carpet surfaces while sucking dry the surface with the extractor recovery hand wand. When this work is done put a portable dehumidifier inside closed trailer and allow it to run for at least 24 hours. The foil backed insulation that Scamp
used since the mid 80's is merely a layer of foil against the fiberglass, a bonded layer of air-cell insulation, and a layer of foil against the back of carpet. The seams of this are taped with aluminum foil and in total should be watertight.
I believe that your mold is retained within the carpet surface and you can kill it with the sanitizer, and remove the remains with the extractor. Good luck, Fx.