If i wish to use old-style interface (like Gnome 2 with global-menu and awn) in Gnome 3, will it be much of customizing and pain, or is just possible with a few clicks?
From the Arch Wiki on Gnome (where Gnome 3 is now in the main repos):
You can enable fallback mode while having gnome-shell installed by opening gnome-control-center. Go to System Info > Graphics and change "Forced Fallback Mode" to ON.
Or, open a terminal and enter: