Disconnect the 12V battery and the car will turn off. When you plug it back in after an hour or so, start the car and it should be back to normal. If you still can't turn off the car, you probably have a bad combo meter which I've heard is expensive. The speedometer should also come back on.
Combo meter is the dashboard assembly. If that goes dark because it is faulty and failing the car will usually not shut off also. if you push the ready button twice it should shut off.
