Upgrading your HD yourself will void the warranty--which is not something you want to risk, given the problems in rev A laptops. The HD is not a user-serviceable part in the MBP. Still, if you're sure to leave to trace and you're willing to open it up again to reinstall the original HD if you ever have to send it back to Applecare, then you're free to gamble with your MBP. You can find the guide at ifixit.com
And be sure to get SATA HD, not an ATA version.