Hello,
I just bought from a friend his iphone 3G. It is locked to his network (t-mobile), and currently his version is 3.0 (7A341).

I read guides and threads about how to upgrade, jailbreak and unlock it, and it seems that eventually most people find themselves without signal (iphone turned into ipod..)

I know I shouldn't upgrade to 3.1 directly from itunes, but download ispw file which is 3.1 for 3G. I got it from:
(please just delete that code if it's illegal to post it, and not my whole post)

I know that then I should use itunes 9 (I have 9.0.1), hold shift while clicking restore, and choose that ipsw file.

As far as I understand, I don't need redsn0w because that file is already jailbreaked, and then only thing I need is to download from cydia ultrasn0w.

Is that is? It sounds quite simple... It won't upgrade my baseband/modem? Why so many people brick their iphone? How will I make sure it won't happen to me?

I would really appreciate your help, and especially if someone already did it and can comment if everything is working correctly for him.

Thanks!

Tom

The iphone can't be locked to tmobile..but anyways why do you want to upgrade to 3.1? seems like such a hassle. Since the iphone has been jailbroken, you can upgrade to 3.1 by using pwnage tool and creating a custom ipsw then use itune to restore from that file. this will allow your phone to use 3.1 without upgrading the baseband.