@billybob : You can change the font by goin to Admin CP > Look and feel> Manage skins > Select your skin > Css tab > ipb_style.css
Here should be the place for font.
Basically every theme, has its own mechanism for fonts.
Some basic themes have the same font for almost every part of the site.
Some have it different for header, for footer, for the code editor, for the navigation section.
So in the ipb_style.css you need to find the desired place where you want to change the font, and work on it.
Best of luck (Y)