I replaced only the front and rear decals on my fiberglass 5er. And that was a chore. A 3M eraser wheel helped as it took off the decal material and a lot of the adhesive came off with the decal shreds. And 3M adhesive remover took off the rest. There as a ghost image on the fiberglass of the old decals so locating the new ones was easy. Getting them flat with all air and water squeegeed out before they dried was some work. But it looked like new again. My side decals were still good.
But I have read on here that the eraser wheel will also take off the paint from aluminum siding. So I guess not an option.