there may be a difference in the cd changers to the newer line of ford radios.
I know my newer radio doesnt even have a changer plug.
I would suggest getting an adaptor,
http://www.logjamelectronics.com/piefrdnpcknnsr.html with this you can run an aftermarket kenwood changer with your current ford radio. it also gives you the option fo the changer or sirius... most of these changers can be had pretty cheaply on ebay. If your a big music buff, i would suggest tracking down a kenwood keg. it can hold 10-20gb of music. i have one and its amazing.