modifying an aftermarket 6-cd changer to connect to the factory stereo
 

My mother recently bought a Cabrio, that the advertisement said had a 6-cd changer. She was really excited, but couldn't get it to work. (she's somewhat technologically impaired.) I messed around with it for a while, and found it works through an FM transmitter, so the CD button is useless. Can I somehow modify this to hook up to the factory standard stereo so my mother can just hit the CD button? The more foolproof the setup is from the driver's perspective, the better.

The system is a Pioneer CDX-FM867 system and its a Mk 4 Cabriolet.

If someone can give me an answer, you probably will be saving me a fortune in headache medicine alone!

Yes, you can hook it up if it's a late model Cabrio. I can't speak to pre-2000. But I did this same thing with our 2001 Cabrio when it was new. There are adaptors made to hook up most all CD changers to the factory head unit. I have an alpine 5 CD changer hooked in. It required only one adapter interface cable made specifically for Alpine to VW. It was 8 years ago so I'm sorry I can't provide more specific info, but try Crutchfield. BTW, I looked for your CD changer there, they show a CDX-FM687 but not a CDX-FM867.