You can replace the sights yourself. Bare bones, all you need is a small hammer, a drift punch, a pair of needle nose pliers, and a non-marring surface upon which to work. Sight pushers are nice to have, especially if you have more than one gun (Brownells and Topglock list sight pushers specifically for the Glock that are reasonably priced). Biggest challenge is getting the new sight properly centered. You want to try what I do, be might guest, but I'll assume no liability if you damage your gun (standard disclaimer) Basically, you just drift out the old rear sight and drift in the new one. I usually go left to right, although I'm unsure if this is really necessary. Remove the rears to the right and put the new sight in from the left. Front sight (for Glock factory plastic sight only): grab the front sight with the needle nose pliers and yank it straight off the slide. Note you will not be able to reuse the front sight if you remove it in this fashion, but I never use these plastic things again anyway. The new front sight in most cases is retained by a small bolt from the bottom (inside) of the slide. I usually coat the threads with blue loc-tite to keep from losing the sight (some people recommend red loc-tite). Make sure the front sight is properly aligned (parallel with the sides of the slide). Let the loc-tite dry for a day or two, then go to the range to see how close you are.
Up to you to decide whether you want to do this or pay somebody a small fee to do it for you.
As always, make doubly sure your gun is UNLOADED