The original wall finish on the Campsters was indoor outdoor carpet. It is adhered to the walls with the standard type of yellow contact cement. That carpeting was installed before the cabinets so if you want to remove all of it then you have to also take out the cabinets.
The quilted wall material was used in the Compaq trailers. They are similar sized popup trailers but were not made by the same company. I believe there is a place to obtain a very similar to the original quilted wall covering. Look for that information in the threads about those trailers.
I own (a $1,500 fixer purchase) needed an all new interior, the cabinets were in very bad shape and the carpet on the walls was saturated with mildew and mold well beyond the point of no return, no hope of ever getting it cleaned out of the material. It had lots of leaks
and was being used as a storage shed for a lot of years in the rainy Pacific NW. So I ripped out the interior, added some furring strips, put in insulation, did moisture barriers then put up 1/8" birch plywood panels. That takes a lot of labor hours but it was worth it for getting some effective heat control, warmer in winter, cooler in summer. I needed that extra insulation because I will be in it full time for several years starting later this fall
My remodel was not quick, easy or inexpensive. But I would make back the financial investment if I were to sell it. But I would not come out ahead if you counted in my labor hours. The only way for me to get that back is to use it and enjoy it for a lot of years.