I have new M&H complete harness, and replacing my old one has been a blast ...it's gone beautifully - great product, identical facory plug ends and colors etc. I'm a little puzzled though about snaking the new dome light wires (orange and white) above, through, and above/behind the headliner space to the trunk. Anyone done it before?

I know how it goes .. as I restored the car myself including the headliner .... it goes from the dome light, directly to the driver side behind the headliner then takes a 90 degree turn and travels back to the rear window and then turns again downward to the trunk area where it plugs into the rear light harness ... Am thinking I borrow an electrical snake for threading wire through drywall cavities .. ? Any tips?

I would try the snake after removing the left interior quarter pannel trim, but be carefull, they're pretty stiff and it could go through the headliner.
There are a few supports up in there it could get snagged on. Hopefull someone else has done it.