Plus one on the advice given. To replace the whole lining you have to pretty much gut the trailer and remove
windows.
One more option to throw out... If you don't mind the R&R of cabinets and
windows and you want a like-new surface appearance, I'm thinking you might keep the foam and add a layer of Scamp's "rat fur" or marine headliner on top (once it's thoroughly clean, voids filled, and loose spots re-glued). I don't know I've heard of anyone doing that, but I personally like the feel and appearance of the headliner over
paint. The foam insulates better than Reflectix, which is what most new builds use under the headliner, and your foam appears to be intact for the most part- just the vinyl is peeling.
I'm curious what others think... Would the added thickness cause any issues with the fit of the cabinets, other than possibly requiring slightly longer rivets?