Troy,
Yes, the door you have won is a Genuine Hummer fuel door.
OEM refers to "Original Equipment Maufacturer," so yes, you are bidding on the Genuine item.
This item is currently available on Hummer-Parts.com for $158.00 --
Hummer Fuel Door Link
Post some pictures after you install it!
Best Regards,
-Justyn
Black '04 H2 -- GOBI Ladder, Corsa, and.... ?