I have a 3GS on version 3.0, no SIM card. I would like to upgrade to 4.x and jailbreak/unlock, but right now I can only upgrade to 4.0.2, for which the jailbreak is not available yet. Trying to Restore to version 4.0.1 gives the message "invalid image". Should I jailbreak now on 3.0 with redsn0w, and wait to upgrade to 4.x later? Anyway for me to get to 4.0.1?