Can a user log in to Drupal, fill out a contribution form to renew their membership, and change their Email address when contributing? Looking for an optimal workflow here. If the email address on the contribution page auto fills with their CiviCRM primary email, and they change it on the form, will that change the address in CiviCRM and/or their linked Drupal account? If not, how could I make this easiest. What happens in my org is that members sometimes have old AOL emails and want to change it with something new when renewing.
Petednz is correct. If a user is logged in, then they can change their CiviCRM e-mail address on a contribution form. This won't change the Drupal address AFAIK; I'd be very surprised if it did.
If you also want to change the Drupal e-mail address, you'll need to write an extension (or hire someone to do it). My Domain Access CiviCRM module is conceptually similar and will get you about 80% of the way there. You can also check out CiviCRM Wordpress Profile Sync for inspiration, since that's the functionality you're looking for, but for Wordpress.