How do I change my gmail account on my t-mobile g1?

I have a tmobile g1 I bought it off craigslist but the guy who sold it to me is still logged in. He gave me his user name and password and i still can figure out how to switch the accounts.

How do I change my gmail account on my t-mobile g1?
10-4
Reply:take the battery out for 30 seconds, turn the phone back on, and then a screen show up where you can login or create a new account Report Abuse