Q: How do I change my rescue email

If you know the answers to your security questions, then from http://support.apple.com/kb/HT5312 :

1. Navigate to appleid.apple.com using your web browser.
2. Click "Manage your account"
3. When prompted, sign in using your Apple ID and password.
4. Click Password & Security
5. You'll be asked to answer 2 of your 3 security questions before you can make any modifications. If you are unable to remember your answers, you can choose to send an email to your rescue email to reset your security questions.
6. After you've validated your identity by correctly answering your security questions, click Edit to the right of your rescue email address.
7. Once you've finished editing your rescue email address, click the Save button directly below the email field.

If you can't remember your answers and don't have access to your current rescue email address then you will need to contact iTunes Support / Apple in your country to get the questions reset.

Contacting Apple about account security : http://support.apple.com/kb/HT5699