Originally Posted by lapicito
Can any Glock armorer do it and what would be the cost?
Yes. It depends, some Glock Armorers will charge for their services. They should be able to order the kit from Glock under Warranty and replace the parts for you once the kit comes in if they don't already have the parts on hand.
You could ask around at your local gun stores if they know a Glock Certified Armorer. You could also look at Glock's website, in the upper right hand corner there's a "Dealer/Range Locator" box where you can enter your zip code and find Glock Stocking Dealers and LE Dealers in your area, they may have an Armorer on staff.
If the trigger bar is coated black, it has the old parts. If it's coated silver, it likely has all of the newest parts.
I'd also check the slide lock spring, the old thinner slide lock springs were more prone to breaking and leaving a broken off piece in the frame that even Glock sometimes can't remove. The new slide lock springs are thicker and less prone to breaking. In the picture below, the old thin slide lock spring is on the left, the new thicker slide lock spring is on the right: