Can I download and play gta san andreas of xbl if I...?

GTA San andreas is available on the games on demand for 1200msp, i just checked and its 2.87gb to download, if you do download it you dont need a disc to play it, you only need the disc of a game that you have installed from disc to a hdd on your console.. ive not seen less than 250gb external for the slim? also i think black ops is still most played at the mo.. although i prefered mw2.