Lot's of good ideas here. I'd get a new Razor blade for your scrapper and use it in conjunction with the hair dryer first to get rid of the plastic and then gently rub the remaining glue off with WD-40. If the hair dryer doesn't do it try WD-40, scrapping, WD-40, scrapping, WD-40, etc.
If that doesn't work PM me and maybe we can work something out
PS: WD-40 is Flamable. Make sure you give it lots of time to evaporate before you start er up.