I replaced the dash myself. Ordered the dash plastic without the monitor hole (both types are in 2001 LYG-30 Parts List) through my local Airstream dealer ($91.00 plus shipping). However the new ones came without the mounting screw holes drilled. Had to use the old broken dash plastic as a template and used a drill press to drill and then countersink the mounting screw holes (holes for the switches, A/C controls, lights and speedometer were thankfully there).
I pulled the front TV and the passenger plastic dash panel to find out where the old Sony cable was routed. It is routed across the length of the dash, through the corner of the curbside windshield support, and then into a trough all along and under the curbside roof. I was unable to pull the old Sony cable out (must be bundled with other wires). Then I ran a steel tape fish down the trough. I can get to the rear of the MoHo, but haven't been able to get around the corner yet. I will try to "fish the fish" through the hole in the rear where the old cable is routed. If I am unable to "fish the fish", I will have to use your method. Appreciate the response.