I appologize in advance...I searched for a while on this forum for a guide on how to upgrade my 3G iPhone from 3.0 to 3.1.3 and could not find one.

Here are the details:

I have (already) jailbroken iPhone 3G that is on the 3.0 firmware. I am a t-mobile customer and a Windows 7 user. I want to upgrade my iPhone from 3.0 to 3.1.3 and maintain the jailbreak and ability to use t-mobile. If you can provide a step-by-step guide on how to do this, I would greatly appreciate it.

Now I can thank you in advance.