I am looking to upgrade the RAM in my Macbook. I currently have the default 1gb (2 512mb stick) and I'm looking to purchase a 1gb stick of ram. My question is, is it wise to have 2 512mb sticks and 1 1gb stick? Also, will my Macbook have enough slots? I just bought this Macbook last week so I have the 2.2Ghz, 1GB, 120GB version.