I actually just purchased & downloaded this successfully from gamestop a couple weeks back (http://www.gamestop.com/xbox-360/gam...ltra-dlc/87596
). As far as the DLC goes, i dont think that will be available unless you previously downloaded it.
For those who have owned this in the past, i would suggest going to https://live.xbox.com/en-US/Download/History
, from there you can re-download anything you have purchased. Hope this helps.