Frustrated with header/menu

I’m so frustrated with the menu in the header of my site. I can’t seem to have an effect on the pages that appear there. It seems to me that there must be an instruction in the code that is telling it what to put there, but I can’t figure it out. Last time I asked about this, I was told that it was <?=wp_list_pages2()?> in the header part of the template, but what does that mean exactly and how can I tell it to do something else?

It’s not taking just top level pages (which is what I want), it’s not taking pages it order, it’s just got a mind of its own. I tried rolling things up into holding pages – no luck. Phooey. Ideas welcome

Site is http://tribeofadmins.com