Updating your AppleID on your iPod Touch
If you find yourself needing to inform Apple you are using a new email address, you don't have to go to AppleID on the website. On your iPod Touch go to Settings, scroll down to and click on iTunes and App Stores, you'll see your AppleID and your current email address, click on your current email address, you'll see a menu, click on View Apple ID. You'll be asked to type in your password and then you'll be able to replace your OLD email address with your NEW email address.