Mafia 2 DLC for the Xbox 360

A few weeks ago my brother moved out and took his very nice PC on which I had been playing Mafia 2. I went ahead and bought Mafia 2 for my Xbox 360. I'm curious as to how the DLC packs work for the game, where I can get them, and how much they are. I'm very new to the Xbox 360 (I'm normally a PC guy) but I do have Live. Any help would be appreciated.