I have an ipod touch 2g (non-mc model) jailbroken at OS 3.0. Is there a "jailbroken update" to take it to 3.1.3, or do I need to download the offical update from Apple, which should turn off the jailbreak, then jailbreak it again? I asusme doing so would wipe out all of my custom configs through cydia and I would have to do it all over?