How do I unlock my iphone 3g running os4?

I am getting a new iphone 4 and would like to unlock my iphone 3g so that another family member can use it by transferring their sim card. I have read that i need to do this before i activate my new phone. I also downloaded the newly updated redsnow. I wasn't sure whether redsnow would unlock it as well as jailbreak it. If someone could let me know if it will unlock my phone or guide me to the proper download that would be great thanks.

p.s. If anyone knows of a good website that guides you through the process that would be great too.

Hi. Don't worry. You can unlock your iPhone 3G without jailbreaking itself. All you need to do is to visit Unlock-Zone.Com and get the remote unlocking service. This method of unlocking an iPhone is safe, simple, affordable, quick and permanent. It doesn't require a jailbreak as I said you earlier. Good luck.