Need: Plastic grocery bag, brass or aluminum punch, hammer, allen wrench for sight, good sturdy vise, and tape.
Check, clear and remove slide. Wrap your slide in tape to protect the finish and mount securely into the vise. Remove the allen screw from rear sight and tap out rear sight from left to right (toward the ejection side.) When it "breaks lose" it will tap out fairly easily but don't go too far until you wrap it in the plastic grocery bag. About 2/3 way out STOP, you will see the "shiny" plunger sring cap starting to get exposed, the only thing holding that and the sping in is the rear sight. You want to make sure you catch them or they will fly to the ends of the earth, that is why I suggest the use of the bag as a backup. Finish tapping out the sight and you will have the plunger, plunger spring, and cap hopefully!!
To reinstall just reverse the order. The tricky part is starting the sight on and then getting the spring and cap back on. I like to have the sight over the opening a little and then "slide" the spring and cap into position. Use the bag especially here because if you let the spring step out sideways it will be gone forever! It takes a little practice to get it back together and a lot of patience!! It would be nice if they would put a keeper ring on the cap for the spring! Just push it down and hold it while you move the sight over the cap. At this point in the beginning of the sight install it moves fairly easily. Finish tapping in and reinstall the allen screw. reassemble and function/safety check.