a little trick ( aside from using a large plastic bag to catch all the flying parts) is when you try and reinstall,, center the plunger and its hole directly UNDER the flat of the blade after you screw on the blade till the head is flush with the end of the screw...look, you will "see" what I mean when it comes to that time.....never lost a plunger yet doing it this way......same holds true if you can get the nut off without having to "break" off the head of the screw, all depends on how good the "staking" job was done, they can and will unscrew "sometimes"
Gotta have a sturdy "split" screwdriver for the slots in the nut, and hold the opposite one, in place, or vice versa............