I have went in and bought night sights and gotten extended slide stops on all of my guns . They rebuilt a used 17 I bought that was missing parts, the gun is my favorite .
+1 on Glock customer service.
Several years ago I bought a dirty G21 that was a LEO trade-in at a Gainesville company. Being a Gen2, I wanted to make sure the "upgrades" (Glock doesn't have recalls as I understand) had been performed on this gun. Also, the mag didn't "jump" out of the gun like the new magazine did. Long trek from Buford to Smyrna, but (once they got me checked in) In about 20 minutes, the armorer brought it back with new front and rear sights (he said they weren't broken, but he said I needed new ones) and 7 other new parts (not including a new magazine, which isn't normally covered under warranty). I was very pleased. No charge.
Problem is, he asked me if I'd seen the (new back then) Glock 30. When I said "no" he stepped out and returned with the G30, showing me how my G21 mags fit that compact .45. Took me about 6 months to save enough $ for my G30, (and to find one in stock) which is now one of my favorite handguns.
They totally rebuilt a 19 for me on Tuesday minus the slide, barrel, and receiver. Everything else was replaced along with two mags. Also got some swag to boot, a couple of stickers and a Glock Travel Mug. Can't beat their service, I'm an armorer And I prefer to go there instead of doing it myself.