...only 1 small command apt-get install gnome-panel
Yeah, I'm lost here as I didn't know gnome-shell 3 came installed by default? I have no
idea about that, but I am surprised you had to install something at all and I certainly didn't mean for you to install anything (it may even be unnecessary
to have done so). I believe Alt+F2 > gnome-shell
should have been run instead, sorry.
I am not sure if you can manage these 2 menus at the same time but it sounds "do-able", I just don't know how. I gnome2 I could edit the gnome-panel properties and add another "Global Menu" or some such.
KDE may even have a plasmoid for a gnome-shell menu feature/function.
...it only runs in terminal. Only one top level menu is allowed it says and a whole bunch of error logs.
Post the relevant logs only if gnome-shell doesn't work and has issues a la gnome-panel.