I'm getting ready to replace my head unit over the weekend and remove the aux. jack. I'll let you know what kind of wiring it has, but as I recall from the wiring diagram, it's a simple three wire connection with a neutral, a left channel and a right channel input. Are you planning on doing a simple 'Y' configuration, or are you going to try to install a switch to go back and forth between the two sources? I figure if you switch the common wire, it should work well.