Nokia 6682 / 6681

Because of problems with my 6682's firmware and/or phone software that was not repaired after a month at the Repair Center, Nokia is sending me a new unit under my warranty. Just what is stored on phone memory and how do I delete sensitive information such as passwords, internet connection log-ins, etc? I guess I should also format the memory card before I send the old unit back.
Thanks.
PAUL