[ubuntu] need help with gnome shell settings

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http://ubuntuforums.org – I have a few questions that I'm hoping you guys can help with. 1/ Having installed gnome-shell (3.4 according to synaptic) and gnome tweak, I can change the window and GTK theme but not the Shell theme, as in the pic. How can I change this? 2/ How do I install gnome shell extensions? 3/ How can I add Shutdown to the settings menu? Cheers. (Hardware)