These guys will warranty it themselves and they are close to you. I have had my truck in the shop here locally and had no problem with repairs. Also, the truck did not perform up to snuff when I took it to the track so they came and got it, took it back to Decatur, fixed it, and shipped it back. No charge. I had the full boat done plus extras. The truck is quick.
http://www.lingenfelter.com/performanceh2_hummer.asp
Speak to Tim Dyer.