Welcome to the 10mm club! You have the most accurate weapon Glock makes other than the G21.
You'll probably want to order some ammo off the internet. The cheapest I've seen is at http://www.natchezss.com. Check out the CCI/Speer 10mm for less than $10.00 for a box of 50. Range ammo runs about $20 a box in my experience.
I recently bought the "hunting" barrel for my G20.
I've been told they weren't making anymore so if you want a real glock barrel like that you might want to try to order it ASAP.