Do I have to use one of these interfaces or a fm modulator to listen to my ipod through my stereo system?

I have a 2007 Escape with a cd changer.

Is there a way I could just splice into the audio in lines from the cd changer and put a simple multi wire switch in from radio shack to switch from cd changer to ipod.

I dont mind having to control my ipod from the actual ipod.

Is this system realy that complicated that I must use a $120 interface?

Sorry if I missed something in all pages on this thread.