You can find tutorials for adding modifications and themes all over the Internet. If you're interested in tutorials and themes, I suggest that you take a look at http://www.vbulletin-faq.com/
-Note: I don't own a copy of VB, so don't ask me for personal support-
I suggest if ya don't know fully what your doing when you mod just hire someone to do it, I learned that the hard way after killing about 3 boards I said forget it and hired someone..lol Well Good luck to ya's..