How to change primary email account for Android phone G1 Dream?

Android phone G1 Dream has only one email account associated with Gmail app. When you start pre-installed Gmail app (not Email), you can directly read your email without login and get notification when you've got mail. This email account is also associated with other applications like Contacts (sync with your email account) and other Google apps. When the phone ownership changes, e.g., you want to give you G1 Dream phone to your spouse since you just bought a Droid, the email account needs to be changed. How can I change the primary email account? How can I remove existing contacts to protect privacy? How can the new owner import his contacts?

Some people suggest we do factory data reset. It is not necessary. Here is how you can do it without factory data reset.

1) Go Menu -> Setting -> Applications -> Manage applications.

2) Gmail Storage -> Clear data.

3) Gmail -> Clear data.

4) Google Apps -> Clear data.

5) Google Search (enhanced) -> Clear data, then your existing contacts and your former email account are removed.

6) Restart Gmail, which will ask you to set up your Google mail account. Now you can set up a new gmail account. Then emails and contacts will be synchronized and shown up shortly.

However, it does not work for Nexus One. On Nexus One, you will not see Gmail storage, Gmail, Google apps, or Google apps item on Menu -> Setting -> Applications -> Manage applications. But for Nexus One, you can associate several email accounts with Gmail app. Here is how you add multiple email accounts to Gmail application on Nexus One.

1) Go Menu -> Setting -> Accounts & sync.

2) Add account and set up another Google email account following the wizard.

3) When you start email, you have one primary account and emails associated with it to read. When you view email, you can select Setting -> Accounts and pick your another email to check emails associated with your other email accounts.