CD Changer for '99 Taurus

I bought a Neo CD Changer for my daughter's '99 4-door Taurus sedan.  I can install the RCU cable adapter to the antenna box and black ground wire to a chassis nut in the trunk (back left).   There is a dangling yellow wire on the cd changer adapter that I need to connect to "constant 12V."  The instructions state: "We recommend connecting the Yellow and black to the same power source going to the head unit to avoid a ground loop."  I see a coax cable and two wire harnesses going into the antenna box in the trunk. There are two female connectors (a 4-pin and another gray rectangular one).  I see no separate GREEN/ YELLOW cables that have been identified in the Vehicle Wiring database as "constant 12V" cables.

Where do I attach the changer's yellow power cable and how do I do it to avoid electrocuting myself?  (slight laugh)

Yellow/red...you'll see it running up along the chassis wall where the ground is attached.  There is also a 12v switched source BLACK/ pink beside it.

.........and don't stand in a puddle of water while holding onto the car while you're tapping into the wire.  Actually, you just disconnect the battery negative terminal anytime you are dealing with electrical wiring.  You would disconnect battery...knick a spot in the wire you want to test...reconnect battery...test wire with meter for 12 v with key on and off (to prove it's constant)...disconnect battery and solder your lead and tape it up...reconnect battery and test the system.

You need a code for that radio???  Is it just a factory tape deck and FM radio?  I have a 98 Mercury Sable/Taurus GS and I've disconnected the battery a few times to hook up my system and the radio never needed a code to start back up.  That's my car though, it might be different in your daughters.