I just installed some indiglo faces in my car.
I grounded them on the metal bar behind the cluster. I beleive there is a screw to the right you can unscrew, loop the wire around and tighten up for a solid ground.
For a dash light on power source, i used the brown wire off the headlight switch i beleive. It came on with the parking lights.
I used a crimp from radio shack that allows you to splice onto the wire without cutting it.