I have done this several times for my apd and pdgt. I bought a second hand pdgt and replaced the bumper, grommets and it looked like new (for a while). Very nice.
drak is correct. It was very painful and frustrating to put on. You'd need the right tool. Initially I planned to change the whole set then after 1 hr I just settled with replacing the one that was broken. LOL.
Don't order just one set. These stuffs are flimsy and don't last long. Order a few and save on shipping.