There are multiple places that make RV decals including some on ebay. Google RV decal. You might get lucky and find an exact replacement. If not, an automotive decal/wrap shop may be able to duplicate yours. As a last resort, you could buy a custom decal with many options for scenery, animals, or somewhat off the wall scenes.
Not to difficult to remove the old ones. Some use a heat gun and plastic scraper. But I had better luck using a 3M Eraser wheel and 3M Adhesive remover.