I have done the auxillary input modification on mine. I will not do it again.
I also have an inline modulator that came with the car kit for my XM radio. I use the inline in my pickup. I temporarily putthe inlineinto the 'Wing just to do a comparison with the pre mod using the inline modulator and the modified input. A good inline gives sound quality that, to my ears, is just as good and you don't have to monkey around with the internals of your radio. In fact just this week I developed a high pitch whine that is present only when the wire from the modification is plugged into the XM reciever. I have not had time to try to figure out the cause of that yet.
Directions were easy to follow (if you have basic electronics knowledge). I did not use a toggle switch to activate the mp3 plug, Radio Shack had a flush surface switch that fit perfectly on the left edge of the radio console nearest the left pocket. Looks like it is factory installed. I love it. Works perfect. The only regret I have is I wish I would have extended the length of the male plug that fits into the mp3 player. My son likes to bring his MP3 and the wire is about 2 feet short of reaching him in the back. Too bad for him, since I choose what we listen to .