How hard is it to install your own Night Sights on a Glock 21?  I'm thinking of replacing the stock sights and am wondering if I should just send it out and have a gunsmith do it.

i installed my own night sites on my model 22, in a hotel room while on TDY. could have just got lucky but it wasnt difficult.  i taped the raer of the slide and used a small punch to tap the rear site in till looked centered, and the front site screwed in.   looking back i probualy should have had someone install them but it  turned out to drive nails.

Its pretty easy. Just remember...To remove the rear sight, tap(with brass punch) or push(with sight tool) from left to right. To install, just the reverse, right to left. Its not hard to tap the rear in with a brass punch, but you may scratch up your slide. I recommend getting a sight tool. I bought the one from Glockmeister.com, it comes with the wrench for the front sight also. And if you buy the tool along with the nite sights, you got a discount. Mine has worked perfectly. I highly recommend it.

Be carefull when tapping and not using a pusher.  The Tritium inserts are fragile and have been know to crack and as a result quit glowing when installed with a punch.

Please, don't try "tapping" them in. It will generally work, but you'll break a set at some point. And it's frustrating to get the rear sight zeroed.

It's expensive, but the tool you need is at Glockmeister.com. (Look under sights, etc.)
It's a sight-installation jig.
Won't break your sights -- allows removal of the old one and install of the new, front and rear.
Also, you can take it to the range to zero it in.
(This is major for me. My gunsmith doesn't zero them, and after he installed a couple for me, I got tired of "tapping" them to hit properly at the range. With the Glockmeister tool, I can precision adjust at the bench.)

If you're only going to install one set of sights, my advice is to have somebody do it who has the proper tool. But, if you plan on installing several sets over time, the tool will pay for itself.

As a Glock armorer for my dept. I have installed many.  I agree with the above posts that you should use a sight pusher and not a punch.  I know people that have gotten away with it but I also know those who have not.  Here is another tip for the front sight: Apply locktite to the threads of the smal front screw and do not put it in the female part of the sight itself.  The reason is that by puting too much in the sight, you can create a hydrolic effect when you tighten the screw and rupture the tritium ampule.  I have seen it happen.  Be careful not to torque the little screw too much.  It is not hard to break.

A sight pusher is the proper way to do it for press fit sights.  Ameriglo's sloped sights are user install with a hex screw, the AO 24/7's(ashley outdoors) are that way too.

Otherwise go to Lonewolf Distributors to get the MGW sight pusher and Glock factory front sight tool.

I threw the XS Night Sights on my Glock and it was incredibly easy to install them