Whirlwind, or any sys 11, is VERY hit or miss if you can safely remove the mylar. If you are inexperienced i would advise not messing with it. if the raised insert is not affecting gameplay I would leave it alone. Remember, the enemy of good is better!
There are alot of really knowledgable people over on pinside who can give you some advice, check for a thread by Vid1900 on playfield restoration.
Really, if you're going to be working on pinball machines at all joining Pinside and seeking out every help thread Vid has posted isn't a bad idea. There are lots of other helpful people, but for tech Vid can't be beat.