Gman: Installing the bigger HD is a doddle, you've actually done most of the procedure in getting your original HD up and running.
The only things you need to watch are:
1. If your not using a TSOP or mod chip, you'll need to use LiveInfo and ConfigMagic to get eeprom info and calculate a new HD Key for the new drive.
2. Locking the new Harddrive (double/treble check the code) the hddlock program generates a text file with the key used to lock the drive keep a copy.
3. Backing up the original HD (HDDriver can be buggy, but if you managed it once you should be okay) Once this is done, lock your original retail drive away, you can now happily screw up your new HD!!!
3. HDDriver restores can sometimes be corrupted, I found nearly all the gamesaves were corrupted on my new HD (this can sometimes be the case when the gamesave puts in a signature based on HD Serial... but not all games), easiest way around this is to format E: using Evox and ftp a copy of your E-drive onto the new HD.
Enough rambling, I don't want to make a post into a tutorial, especially with plenty of good tutorials out there already.