How bad is the mylar on your playfield and does it have to be removed for the sake of game play or because you want to?  For me personally I am happy to put up with old mylar if it isnt affecting game play and means the playfield artwork will remain intact.

I have heard of guys leaving the playfield in the sun on a very hot day to heat up the mylar.  I have used the heat gun method but that was on a clear coated playfield and it worked well.

If you do remove the mylar just ensure you do it very very slowly.