If you have a contact that is currently on an email campaign with a bad email address, if you change the contact record to the correct email address, the emails that go out in the future on the campaign will go to the new email address.
Although, what you probably will want to do is perform kind of a "reset" for this contact on the email campaign and you can do that by going to the list of contacts on the email campaign and remove the contact (or go to the contact detail record and click remove in section Email Campaigns).
After you have removed the contact from the campaign and corrected the email address, then re-add the contact to the email campaign. When you do this, the contact will then be put at the very beginning of the email campaign with the correct email address.