You can change your AppleID/e-mail address. In iTunes on the Menu Bar go to Store/View my Apple ID. It'll take you to your account page in iTunes. Where it says Apple ID(your e-mail address) there is a link to edit that information. It shows your current e-mail and password/verify password. Below that is a link to change your security questions and other Apple ID details appleid.apple.com.
On that page it says if you change your e-mail address it'll send a verification e-mail to that address.. and that new Apple ID/e-mail address will be used to access all Apple services(iTunes etc)