in gnome 3 it isn't alt+F2. Either the super key (under Windoze systems this key is called "Windows key") or via the mouse movement to the right-hand top side. But it's right that another key combination works as well, but I don't use it.
IMHO the default appearance of gnome 3 is fine. I'm not a configuration freak. I even keep the desktop background image usually, except if it's too ugly.

