Seriously, I need a simple version.
Unlocking iPhone3G for Dummies, if you will.

I recently came to be the owner of an iPhone 3G, thanks to a friend who no longer needed his.

I have Tmobile, and I would love to unlock the iPhone and use it.
All I know about my iPhone 3G is this...

Firmware version 3.1.2 [7D11]
Modem version 5.15.04

I've tried downloading ultrasn0w and yellowsn0w.
But I really don't know what I'm doing.. So, instead of screwing up the phone, i need help!!!!...
so... Help... please?