I don't think you can change the password from the phone. If you changed it via computer, then you might have to factory reset the phone in order to change the Gmail address and password.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
I want to make sure you're able to successfully use your Gmail. I need to first confirm if the password was changed on the computer already. If so please follow the steps on http://bit.ly/SJqtzd to update it on the phone. If the password needs to be changed go to your browser and go to http://gmail.com and login to your account. You can then go change it through the same process as a computer and update it with the steps provided.
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