Ok, I am a total computer noob, so I barely know what RAM is. All I know is that it will make the computer faster, and since I run VMWare Fusion and multiple Apps at once, it's kind of necessary to me. Now, to upgrade to 4GB, do I have to add another 2GB RAM? Or get rid of the one in there and get a whole new 4GB one? Where is the cheapest place to buy RAM? I got my Macbook in Summer of 2008 if that makes a difference. Thank you for your help!