2) there are plenty of sections here to help you with it. find one. steps:
DL 3.0, run redsnow, install cydia, jailbreak, install ultrasn0w repo, install ultrasno0w, reboot, use. but search for specifics.
1) Update to a 3.0 official IPSW. Not a jailbroken one. An official one. I know, it's weird.
2) Then, restore your phone using a jailbroken 3.0 IPSW. Then install ultrasn0w and you'll be jailbroken and unlocked.
Make sure you use a 3.0 IPSW. If you use 3.1 or 3.1.2, your phone will be carrier locked, perhaps forever.
If you want to upgrade to 3.1 or 3.1.2, update to 3.0 official and then jailbreak a 3.1 or 3.1.2 and restore using that.
The reason you want to update to 3.0 official is because you need to update your baseband to 04.26.something. The 2.1 baseband isn't unlockable by Ultrasn0w and there's no reason to still be using it.