IF they put formica over the original sideart, the chances of you getting the glue off without wrecking it are slim, and not a chance in hell.
Sorry to sound so pessimistic, but there's a reason you shouldn't touch the glued surfaces together until you are positive everything's lined up right.

If the sideart is on vinyl, a heatgun will only guarantee you'll wreck it. If it's painted on, you MAY be able to use the heatgun. If you're trying to save the artwork, though, using a heatgun is like using a jackhammer to clear the ice off your kitchen windows.