Hello and welcome to The iPhone Blog forums! Please take a moment to check out the thread below. It will point you in the right direction for some of the questions you may have.
I also moved your thread in the appropriate forum. In this forum you can find all of your jailbreakin/unlocking questions. As for unlocking a 3g I'd say no simply because the only method to do so at the moment is a SIMable hack which is not stable and I would not tell my worst enemy to use that. We are still waiting for a software unlock from the Dev Team. And at this point who knows if it is even possible.
Ya it's possible to unlock your iPhone 3g from network lock.To unlock visit Unlock-zone.com here they help you to unlock your iPhone using remote unlocking service.