My Iphone4 is with T-mobile. I unlocked and jailbroke it with iso 4.02 and baseband 01.59. I have never upgraded the firmware since the beginning. I worry about preserving the baseband in order to unlock again after the upgrade. But I think it's time for me to upgrade it for ISO5. I tried to read as much as I could in the forum. But I still uncertain about the steps.

From my understanding, I should

1. Preserve the baseband. Software? Not exactly know the steps here.

2. Download ISO5 or upgrade directly from iTune. This will lock my IP4 from Tmobile.

3. Use ultrasn0w or redsn0w to jaibreak

4. Use Gevey pro or ultra to unlock

I am searching for a complete step by step instruction for a long time. But I don't have any luck so far. Please help!!!!