R.M.,
Honestly....its probably cheaper and less of a hastle to install an aftermarket changer, but depending on your setup, if its just plug and play, spending $250 on a used changer might be the better option. My changer went bad in my 95 M8, and instead of dealing with continued stock changer failures, I purchased a Sony Xplode and used the factory changer harness for power/ground and it uses a FM modulator that plugs into the factory antenna plug in the back of the stock head unit. I paid $150 NEW on ebay and it took about 45 minutes to install.
As far as model number for your vehicle, I would suggest calling a Ford/Lincoln dealership and give them your VIN# and they'll give you a part number. I believe a lot of the FLM cars used Sony's, but they fail a lot.