What is the build number mine needs? is there a way to find this out?
That retail disk in the Apple Store is 10.6.3 and you will need 10.6.6. That grey OEM installer they sell you will be 10.6.6. After you erase the disk and install that, just run software update and that will get you to 10.6.8 along with the App Store app that came with 10.6.8.