Ok, the factory six disk changer would not work due to the inability to hook it to a aftermarket HU. A changer is not hard to install at all. You have the power contol bos that has 3 wires. constant, remote, and ground. Then you will have the FM modulator which has an antenna wire that plugs into the HU and a wire that you plug the real antenna wire into. then you will have a thick cable which sends the signal to the changer. It will come from the control box and go to the changer itself. That is all there is other than the remote control. The only downfall to a cd changer is that they skip alot worse than most HU's. With them being bolted directly to a surface that does not give any at all, they will respond to every bump or pothole that you feel. Hope this helps.
Also get a name brand changer if you do get one. A really cheap noname will perform horrible most likely.