D.E.Bishop...You've certainly given us important things to think about before our new install. Thank you! As with many threads, this one has produced a wider variety of information than just an answer to my original question!
I remember I had a heckuva time figuring out the audio/video setup of our previous used motorhome when we first bought it!
Earlier in the year, we were at an RV park for a few months and had cable. We actually brought a small HD TV from home and set it on the dash, connected to the cable bypassing the switch box. So I do know that the incoming cable worked.