Huge Nav Buttons

Hey all! I’m a High School student setting up a website for my school’s newspaper next year, and the CSS and HTML editing has gotten me feeling a bit over my head. Any help is greatly appreciated.

The site is currently up at theo.clanteam.com, so you can see what it looks like currently. The goal is to get rid of the nav bar, and replace it with three or so giant buttons to fill the white space to the right of the letterhead. Here’s a rough draft of what I’d like it to look like: http://bit.ly/cx6njh.

Any help with how I would go about coding that?