Easiest way there is. (
Must already be rooted...)
#1. Download Rom manager, (Paid or free. I would go with the paid version, its absolutely worth the $3. But the free one is fine also) Make sure to open the app once to make sure its all in order and that whatever license/warnings have been agreed to.
#2. Go to
here (Pete's site) on your phones browser and download GPA12 from the link he provides.
#3. When download is complete, pull down your task bar and tap said notification. When you do this, it will ask if you want to use Rom manager, click yes. (Don't forget to make a
BACKUP!!!, and wipe)
#4. After it installs, (remember the first boot after a new install will be a little longer than normal, be patient.) Go back to his site and install one of the recommended kernels (use the same install method as above,
minus the backup and wipe)
#5. Enjoy your Gingerbread goodness. Just remember, its just Vanilla, no real frills, just a newer and better, (in most cases) version of Andriod than most of your friends will have for a while still.
(If you skip looking at the notification, and just go into Rom manager, go to "install rom from SD card" and find "GPA12DEODEXED.zip" in your "download/" folder and select that, will do the same thing as step #3.)