first of all, i would advise you to read. alot.
unrar files, the "install" them as shown in my sig
you'll want a dashboard, xbmc, dvd2xbox, and whatever else you need.
great things...uhhh, you can back up games, play homebrew games and use homebrew apps. you can mod some games. you can use linux. you can play dvds and basically all media with xbmc.