While PC and PlayStation 3 gamers will be receiving their Citadel DLC in a single file download, for some strange reason, Xbox 360 gamers will have their Citadel DLC split into two separate download packs. Bioware says that the download size of the DLC is too big compared to the previous DLC packs, resulting in the decision to split the file into two downloads. You will only have to pay for the DLC once though.
Bioware posted on its Mass Effect 3: Citadel FAQ, "For Xbox 360 users, the Citadel DLC pack will come as 2 downloads on Xbox Live. ME3 Citadel is larger than our previous DLC packs, so it had to be split into 2 downloads. The first pack is priced at $14.99 and the second pack is tagged as free. Players need to purchase and download pack 1, then download pack 2 at no additional cost." The FAQ continued to say that you can download pack 2 without downloading the first one, but users will only receive an error message that will redirect them to download pack #1.
Players will be able to access the Citadel DLC download after they stop the Cerberus coup attempt on the citadel. You do not have to complete the entire game before being able to access the DLC. You will, however, have to meet the characters in the original storyline before you can interact with them in the Citadel DLC. The game will have no effect on the ending, or the extended-endings of Mass Effect 3.
The DLC expands the longevity of Mass Effect 3 and should keep many avid fans happy. The game will also have a few tie-ins with Mass Effect 3's upcoming comic series, Mass Effect: Foundation, which is a comic book series that will go back through the existing stories in the Mass Effect universe and elaborate on them more. The Citadel DLC will be available on March 5th on all platforms.