Stickers on poly? You should be safe to peel them off as well as you can and use lighter fluid to take off the residue. Nail polish remover also works but may cloud the finish. Or may not cloud the finish.
WD-40
Seems odd but seriously works like magic. I had a sticker on the back of a strat for 8-9 years which i removed before selling it. I tried everything to gently get the **** left behind off and nothing worked until someone suggested wd-40. In 2 minutes the gunk was gone for good and no sign there had ever been a sticker there....