Pretty crafty..
You can jailbreak to 3.1, because from what I gather, 3.0 and 3.0.1 ECID's are no longer being signed by Apple since 3.1 dropped.. so I don't believe your 3.0.1 info is going to get stored to Cydia.
The best you're going to get is, JB and update to 3.1, then do the Cydia thing which will house your info for 3.1 on file for future endeavors..