1. There is a way to turn off the email notificatin functionality in the admin panel. You would have to have a mail server setup (SMTP), something I have never done. That's what will give you errors.
2. No clue
3. http://www.phpbb.com/styles/ or download gimp or get photoshop and learn how to edit the graphics yourself. Then you can learn how to edit the code to move stuff around.