I have recently purchased a 2006 f-250 and would like to use my iPod with the factory head unit. I've noticed a aux. button on the head unit, how or can an aux. input for an iPod work. I've taken the dash and the radio out and could not find a plug for the aux. cable.

 

Try this site. Only place that has any in stock that I could find. Ordered a new one today.
FRD04-AUX auxiliary audio input Ford radio Mustang F150 F250 fusion can buss aux adapter expedition
Mine old one lasted 13 mos. It's been suggested to install a switch to turn the unit off when not using it. I will be heeding that advise this time.
To install:
Dash pops off. Move shift lever to Low first, w/park brake set.
Unbolt radio. 2 ea 10mm if I remember correctly.
Remove rectangle plug, rear of radio.
Plug wire harness in accordingly.
Connect pwr and grnd.
Reinstall radio/dash

 

My bad. Welcome to FTE.