I can give some light on 2 of your questions, but have no idea what used to be there.(#2)
One thought on this would be like in our case, when I added the new TV the cable was to short since the TV plug is about 6" farther away then on the old truck.
#1 The color code should be standard, since the connectors come with a color code chart.
#3 Check with your local RV supply store. I have seen 6 ft sections with connector and cable. When I did mine I found a 4 wire section of wire and since the other 3 wires had different gage wire, I just bought the wire.
I staggered the splices so the were separate. and At Radio Shack I bought shrink tube after wrapping the wire in electric tape, the shrink tube was added and shrunk. less chance for water getting in.
Jim (SSG US Army Ret.) and Cheri (TSG Phx ANG Ret.) Mesa, AZ
2006 Dodge Ram 2500 HD Mega Cab Diesel | 2005 Honda Goldwing | 2006 35' Dune Chaser 5th Wheel