What hard drive should I get?

I have a standard 160GB Macbook from the year 2008. For the first year it quickly became apparent that 160GB was noway near enough space as I use it for almost everything from recording music to making short films. So naturally it filled up quite fast. At the end of the year I bought a 500GB seagate external hard drive which is pretty much the amount I need to keep me going well for the next few years. However, I quickly became pissed off with having to cart it around everywhere and it randomly decides to disconnect. So I'm thinking of buying an internal hard drive, but my problem is that I've heard the maximum size for my type of macbook is 320GB which isn't enough. And I've heard it cannot have a 500GB hard drive as the RPM will cause it to overheat. Any suggestions on what to do would be appreciated thanks