I guess when it comes to mylar removal, you need to make a decision of whether its cosmetic vs playability and do a risk assessment.

For me, with my T2 it was affecting game play and being diamond coated there is a level of protection from lifting paint / decals.  PinballGod, hopefully yours was put down by a keen operator to redue wear.  The first lot I took off, I did very carefully with a hair dryer (heat gun bought since).  A LOT of glue residue was left, but I did it very carefully and slowly.

The second lot of mylar (which I installed) - newer vinyl, came off extremely easy and left virtually no glue (was a lot thinner than previous stuff).

My Police Force - overall the mylar is not too bad, although some minor bubbles over inserts.  I've read about using a syringe to inject clear into it, then flatten.  If I can test this method on a dead playfield with mylar I'll give it a shot.  I've read too many horror stories about mylar removal on late 80's Williams machines (ie F14, Police Force, Taxi etc).  Also, I don't believe a decal set is available either. 

I can point you in the right direction for insert decals.  I've had bad ones and good ones (latest certainly the best I've had).