Hey yukafls, I`m going to give you a free bump and spread this valuable bit of info with you (as its not mentioned in your OP):
The Fallout 3 DLC package (with the Pitt and Operation Anchorage) is a Disc, not a code.
Its also worth mentioning that the disc can be installed on an unlimited amount of xbox 360s. SO basically, lets say you install it to your hard drive (takes about 10 minutes), you can give it to a friend/sell it, and they can install it on their HD....and the cycle continues. So its a re-usable disc.