First of all you should update to MIOS V1.9 and beta15, because I can see an expired menu structure; programming details are different in the meantime, and v1.7a has some anoying bugs as well. So, it doesn’t make sense to work on this old version anymore.
The page layout can be customized in cs_menu.inc, CS_MENU_Handler_MainPage and CS_MENU_Page_Root