Jailbreaking and Unlocking iPhone 3G Help?

[Skot]

Hello, i don't usually ask for help on here but i've searched through several threads and nothing seems to be working. My friend has given me his iPhone 3G to Unlock and jailbreak for him. He wanted the software updated to iOS4 if possible too. It's on 3.1.2 and currently jailbroken, although using ultrasn0w the sim cards don't seem to be recognised as i still recieve 'No Service' after hard resets and re-installs of ultrasn0w? I've downloaded the firmware for 4.0, 4.0.1 and 4.1 for the 3G and i was wondering how i'd go about updating from 3.1.2 to 4.0 or 4.0.1 as apple stopped signing these a while ago and i believe there is no unlock yet for 4.1 devices. My plan is to update and wipe the phone to 4.0(.1) and jailbreak and try the unlock again to see if i can have any success?
The phone is an old MB model and i'm not too sure why the unlock wasnt working. I'm also using a Mac computer so any software required, could you please tell me what's available for macs.
I appreciate your help, thanks.

 

[iPhone-power]

Hello, i don't usually ask for help on here but i've searched through several threads and nothing seems to be working. My friend has given me his iPhone 3G to Unlock and jailbreak for him. He wanted the software updated to iOS4 if possible too. It's on 3.1.2 and currently jailbroken, although using ultrasn0w the sim cards don't seem to be recognised as i still recieve 'No Service' after hard resets and re-installs of ultrasn0w? I've downloaded the firmware for 4.0, 4.0.1 and 4.1 for the 3G and i was wondering how i'd go about updating from 3.1.2 to 4.0 or 4.0.1 as apple stopped signing these a while ago and i believe there is no unlock yet for 4.1 devices. My plan is to update and wipe the phone to 4.0(.1) and jailbreak and try the unlock again to see if i can have any success?
The phone is an old MB model and i'm not too sure why the unlock wasnt working. I'm also using a Mac computer so any software required, could you please tell me what's available for macs.
I appreciate your help, thanks.

According to most reports, a 3G crawls on 4.0, 4.0.1 and 4.0.2. A 3G apparently runs much better on 4.1

A 3G needs hashes saved to be updated to 4.0, 4.0.1 or 4.0.2.
If you update to 4.1, the baseband gets updated and cannot be unlocked.

If you decide to update to 4.0.x, you can use Redsn0w to jailbreak a 3G then Ultrasn0w to unlock. Get a tutorial from iClarified.

 

[Applejuiced]

Did you make sure 3G was turned to off if you were trying to use it on Tmobile USA?

 

[Skot]

Luckily, there's SHSH's saved for 4.0, 4.0.1, 4.0.2 saved. How do i update to them from 3.1.2 without iTunes?
And yes, i do keep 3G turned off.