Will probably need to finish at least the back of the bow. Depends what kind of glue was used. Generally, you can run a single edge razor blade under the skins to separate them from the limbs. The blade will take off some glue, but not all. If contact cement was used, you can probably clean it up/off with denatured alcohol. The underlying finish should be OK, though perhaps a bit duller. A coat of car wax would give it wome lustre.
Of course, if the person sanded the limbs before putting the skins on, they can be very dull and even scratched. If that's the case, and'or if a harder glue was used, light sanding with 220, then 320 and probably 400, always with a sanding block, will prepare the surface for refinishing. Then, something like a half dozen coats of hand rubbed birchwood casey gunstock finish will make it look like new. I also use Helmsman satin spray urathane. It's less shiny. It may take a little elbow grease, but it's not a difficult job. Good luck.