Hey bro, great to have you! Feel free to pimp the 100 MAN LAN... we have groups from state college, mechanicsburg, Lock Haven etc coming!
Back to your question. PHP Nuke, you need to go into the /themes/yourtheme/header.html file to change the way the header looks on all of the nuke pages.
If you open it in dreamweaver (or whatever html editor you use) and if you can view it as "design" rather than code. You will see the table layout.
Good luck!