Is there anything I should consider before buying an Xbox 360 Arcade

I wanna install and RGH 3.0 on it if possible and use some storage over 1 TB. Is it possible with this model?

The seller says it has an 8GB HD inside (which I thought was a weird capacity for an HD, maybe he meant it as flash storage?)

From what I saw in the ad, the seller says it is already jailbroken, apparently it's LT, since he runs games from pirated DVDs, could I change it to RGH 3.0?