I just finished last night the new navigation and template system for this site. It is coded from scratch for the navigation style above — a main level and sub navigation links below.
The template for the site is now also all controlled by one file, so making updates should be easy. Adding a new page means copying a new PHP file, adding the new content, then updating the navigation template to include a reference to the page.
I’ll probably post the PHP code for this soon. It doesn’t require any database or special functionality, other than a familiarity with how PHP works.