To change your email address, go to the Discussion List page and choose your list. Then go down to the "Subscribers" section and put in your email address (the one you subscribed to the Discussion List with originally) and press the Edit Options button. Go to the "Unsubscribing" section and put in your password. You are now unsubscribed from the list and will no longer receive email posts to your old email address.
Now Re-subscribe to the Discussion List with your new email address. Go back to the Discussion List page and after choosing your list, under the "Subscribing to" section put in the NEW email address which you want the posts to go to. You will also need to put in your password twice and hit the Submit button. You are now re-subscribed to the Discussion List.