Here are links to the becker USA site. They have kits to get you an aux input but ... you will/may lose your ability to use the CD changer. You could probably get past that with a little wiring trickery. I installed one for XM works great about 2 hours work tops.
They also have cell phone kits which may get you what you want. Actually pretty cheap about $20 or so. The parts guy is real helpful and they will send instruction which will get you there if you have any basic understanding of radios and cars.
http://members4.boardhost.com/beckerboard/msg/9492.html
http://www.beckerautosound.com/
If you are into blutooth parrot has some car kits that will work but they cost some $$
Hope this helps.
ATB,
Tom