no for the iphone 3g i think you use redsn0w but dont upgrade to 4.1 on the iphone 3g iphone firmware lags so badly you will regret putting it on there, unless you already have..
iClarified - iPhone - How to Jailbreak Your iPhone 3G Using RedSn0w (Windows) [4.1]
iClarified - iPhone - How to Jailbreak Your iPhone 3G Using RedSn0w (Mac) [4.1]