Conagher, your G17 might be eligible for some updated parts. If the serial number is in this range, it is:
AA through XG, inclusive
If so, the parts are:
Extractor
Spring-loaded bearing1
Firing pin safety and spring
Firing pin / striker
Trigger bar
You can find more info here...on the G17 and other models that may have a parts upgrade.
There are also pictures of each part showing the old and new parts, so you can check to see which you have installed.
You can install these parts yourself as there is no fitting required, but you might want a good source of instructions on how to disassemble a Glock. I use the Glock DVDs from AGi
http://www.americangunsmith.com/app/products/view/2/Glockbut you might be able to find a YouTube Vid showing disassembly.
The DVD covers a lot more than disassembly, but unless you want to pay for the extra good information, try YouTube.
I called Glock and told them I would install the parts myself on my G17 and G23 and G21. I needed to send the G21 slide in for recutting of the extractor slot but other than that, they are all just drop in parts.
Take care.