I think you need a special tool.
a phillips to get the recoil pad off and a screwdriver to remove the stock screw.
the supermags setup with the raised rifle sites/red dot do fine with that cheek piece in the stock because line of sight is elevated and your head position is proper.
I agree with bill though, for RH shooting at least, if you're changing out one on a regular 870 with the bead or you've added the slip-on fiber optic, I can't get low enough and once you do, it'll bust your cheek for sure.