Where is the dome wire and the ground?

I am installing leds in the cup holders and the foot wells of my taco. I would like the leds to turn on when I unlock, lock or open the doors of my taco. Where is the dome light wire located in the interior of the truck. Also where is a screw or something else that is connected to the frame of the truck that I could connect my leds to(also in the interior and also easy to get to)?

 

there is a constant hot and two grounds going to the dome. one it always grounded the other is on a relay of some sort.
heres a post that may help you
http://www.tacomaworld.com/forum/technical-chat/4838-cheap-free-mods-18.html#post297835