Sounds like you are good to go. So... Once you have the old HD out match the jumpers on the new HD to the old one. This is usually cable-select. When the new HD is installed you can boot from the OS X installer disc. Most new HDs come formated for Windows. When you boot with the X install disc early in the install procedure it will give the option to format the new disk. When you do this take the step to install the OS 9 drivers as well. That way you can also boot from OS 9 as well as X. (Even if you don't plan to install OS 9 this is a good step to do now.)