Upgrading to iOS4 on a 3G
I am very new to the whole jailbroken and unlocked iPhone scene, so I would like to get the most current information before I attempt this.
The facts: This is a 3G already unlocked and running on Tmobile. I bought the phone in this condition, but blackra1n is installed, so I guess it was done with that. It is currently running 3.1.2(7D11), with modem firmware 5.11.07.
I want to upgrade to some version of iOS4, but am a bit worried about losing the unlock, as that would be a disaster.
Any tips on how I should go about this, and/or any pitfalls I may encounter?
Thanks in advance.