They sometimes will come right off, sometimes they have to be pressed off. If you want to try it yourself, you knock the roll pin out of it and see if it comes off. If not, you could try some heat from a torch to expand it enough so it'll come off and the same thing if you put on the other, then put the roll pin back in. If it doesn't budge, even with heat, don't force it and take it to a machine shop where they'll press the old off and press the new on.