hard wiring V1 radar detector

[schumi]

I would like to hard wire my Valentine 1 radar detector into the wiring of my 1987 300E. I would like to tap into the wiring up by the headliner/rear view mirror (e.g., the wiring for the sunroof or dome/map/seatbelt reminder lights). Has anyone done this who could give me info re: how to access the wiring up there and what wires to use (I know I need to tap into one ground and one wire that is hot when the ignition is turned on). Thanks for any help.