Graphics and ram upgrade

[bennnyw]

Hello,
I recently bought this computer

http://www.bestbuy.com/site/Gateway+-+Desktop+/+Intel%26%23174%3B+Core%26%23153%3B+i3+Processor+/+6GB+Memory+/+1TB+Hard+Drive/3152445.p?id=1218380507379&skuId=3152445

My question is what would i be looking for in buying a graphics card that i can be sure would fit, and also perhaps what i would want for RAM.

 

[bennnyw]

I even bought a sound card and still nothing. Im also not sure of the original intel graphics that i uninstalled

 

[bennnyw]

I have searched through the forums, and i do not have any devices listed under the sound devices as people describe, even after i select show disabled devices. But they show up fine in the device manager. so i am at a loss.