You can have dropdown menus but you cannot have one skin for the menu and another for the site. Where did you find that information?
You're in luck that the art42-businessblue2 skin supports dropdown menus out of the box. All you need to do is create (or move) pages under top level pages and the dropdowns will automatically work. There's an old video on this page which shows how to move pages around. If you want a nicer page manager, consider supporting the project by purchasing Page Manager Pro.