What to upgrade and unlock old 3G (3.0) - what are the best steps?

[brasskey]

What would be the best steps to upgrade an older 3G to as new a software version as safely possible and unlock? I would like to move a SIM card from a Razr that was damaged to my old 3G without upgrading the plan ($30 data/month charge). Is that possible? Below are the specs on the phone:

iPhone 3G
Version 3.0 (7A341)
Carrier AT&T 5.5
Model MB048LL
Modem Firmware 04.26.08

EDIT: Meant to say "want to upgrade..." in title

 

[Junkboxy]

If u r looking for a step-by-step tutorial, I roll with those on iClarified. If you just want to unlock your phone as is, then find the right tutorials with the right variables in the title, i.e. 3G and OS 3.0. I believe you can do the quicker jailbreak known as RedSn0w, and then you have the capability to unlock via UltraSn0w, which is described in it's own tutorial.

On a side note: My two experiences on version 4.X on a 3G were inferior to the version 3.0. I caution against upgrading to 4.X. 4.0 = slow, and 4.1 = battery hog (though it may be the fault of multitasking enabled)

 

[brasskey]

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Thanks for the help. I'll try those steps.