You can change your email address using the "profile" button under the "My Account" tab. In fact you can register more than one address with PayPal (from their help pages)
Q: I use more than 1 email address. How many email addresses may I add to my account?

A: You are allowed to have up to eight email addresses registered with your account. Please note that you may not add an email address that is currently registered to another PayPal account.

Hope this helps....

Chas