Soon to be Owner of 360 quick questions

Hi guys just some quick questions about a 360 my friend is going to sale to me. 175 bucks and comes with two controllers, gears of war, halo 3, cod 4, so i think its a great deal. First off he says its 20gb with a hardddrive so I believe that is the older core bundle im not sure I maybe wrong. My question is that can you upgrade a x-box 360 harddrive and what type does it take. Because what im wondering is i just upgraded my ps3 harddrive and it takes a sata 2.5 inch notebook and very easy to do. So im wondering is the x-box the the same type of harddrive or are there any suggestions on ones that I can buy to up the space. Because if its the same type i'll place the 60gb I got from my ps3 and play it in my x-box but i bet thats unlikely to happen? The reason im worried is because on ps3 there are alot of mandatory installs that take up about 5gb each and if x-box dont have many of those then I'll be ok. But I still buy alot of games so 20gb just dont feel like it would be enough for me.

Any advice will be greatly appreciated!

Well placing a ps3 hard drive wouldn't work but there is another type of hard drive for the 360 but, the 20 gb should be enough anyway since you are just starting off.

On a side note you may wanna get up 25 more dollars and just buy a new system because if you catch the RROD on a used sytem you're out of luck

I rather buy it new because of RROD. I am on my fifth xbox360 and im pissed and im waiting 2 get it back. Im buying a new Xbox360 soon around when Gears 2 is realeasd.