Once you have paid for (or downloaded

) the 2.0 update which costed $10, then you can update to 2.1 or 2.2.
So you can:
-Buy it from iTunes, and then from there simply click update to 2.2
- or download it. If you download it, you have to Shift+click restore, then select the 2.0 downloaded firmware. Then once it's restored to 2.0 firmware, update on iTunes to 2.2
From there go to Quickpwn and Jailbreak your ipod. There are some step by step guides in my signature if you like.