Welcome, Margaret! Congratulations on the "new" Scamp!
Regarding the walls... Some more information would be helpful, like the model year. Early units, through the mid-80's, used Ensolite on the walls, closed cell foam with a bonded vinyl surface, sometimes referred to by its nickname, "elephant hide." Since the mid-80's they have used marine headliner over foil bubble wrap. The headliner is a fuzzy, carpet-like material nick-named "rat fur" hereabouts. Designed for marine applications, it does not absorb moisture or odors and resists mildew and mold. (There may have been a brief transition in which they used some other lining material.)
The lining serves a number of important functions: controlling light
and sound, preventing condensation in colder weather, and adding some insulation. Bare painted fiberglass gives up most of those benefits. Both Ensolite and headliner are very sturdy and cleanable. Personally, I would do everything I could to save it first before ripping it out.
Tell us, or better yet, show us what you have and you'll get advice on how best to attempt a rescue operation.