Just like tomdotcom said, check out the youtube tutorial on this. It's pretty easy to do, but sometimes I've found depending on the size of hole in the new plastic I've had to ream the hole a bit bigger on the plastic so the stand-off "snaps" into place easier. If you can, practice on a junk plastic until you get the hang of it.
Sorry I can't post the link to this procedure, we can't see youtube here at work