Masking film should just peel off. Sometimes it comes off in little bitty pieces, but it should come off. Try a wood toothpick and try and pop up a corner. If you can get it started you should be able to grab it with tweezers and peel it off.
You might also try sticking some really sticky tape on it and see if that will lift it. Just be careful of the areas that you don't want lifted!
Just thinking out loud here, but if that doesn't work you might try Goo Gone. Not sure if that will do anything or not, but it might.