hi i have a 03 4.6 with tv on nav with a dvd player in the armrest and the audio coming through a fm modulator. I am installing a aux input to use that as my new source and getting rid of the fm modulator. i am only tapping into the aux input so i need a relay switch so multiple sources are not on at the same time. The switch is where my problem is and wondering if i could get some insight on how to hook it up???