I have over 160 gigs of music but was limited to 13 cds (in dash and changer) in my 2004 C5. Hell when did they finally start putting a line in jack in the Vettes 2008? My Daughter has a 2005 Civic and it has one. Anyway I tried the $80 top of the line FM modulator and it sounded terrible. The guys at the local car audio said I could go with one of the modulators that plugs into the changer harness but they said the innerface wasn't that good for a large library and the thing even doing half of what it was suppose to was a 50-50 crapshoot. And that was going to run $120-$175. I don't care about charging or innerface I just want a "line in". Well Corvette Forum to the rescue. In fact I Googled my wants and it pointed me to CF where I found the schematic (link below) using the relay method. Radioshack doesn't carry the relay anymore but I found one at the local electronics surplus store for $3.50. I also spent $3.50 on an illumitated switch and $3.00 on a bag of two 1/8'' stereo jacks. I had some RCA audio cords laying around. So all in all let's say I had about $15 wrapped up in materials. If you don't have a surplus electronics "get lucky store" around you Google "12 volt four pole relay" they're around $7. Well it works great and it is very minor sugery to the car. Remove the fusebox cover and the snap off piece of plastic at the bottom of the door jamb. I used a "switched" empty fuse slot believe it was #20 "bottom slot" and ran a ground from the seat bolt. Drilled one small hole in back of glove box for wires and I'ts good to go. The one requirement is you must have the aux cd changer and unlike the the other harness pluginners the changer stays and is still functional. In fact it has to stay in. The radio has to see the changer to work. What your really doing is tricking the car into thinking its playing a cd. Infact it really is spinning one but the signal is coming from the Ipod.
http://http://www.pqtsi.com/sedona/vetmp3.pdf
Hey if this link doesn't work it's in the Sticky in the audio section

I'm stoked and thanks again CF