I used a CD unit from another Ford, a "FIESTA" I think that this model is only out in latin america, well anyway, it works...
Both have round volume control knob, but, the real problem is the plug back there... eventhough that the volume control was the same, the plug was tottaly different... so it's not a bolt on/plug in mod...
My Solution:
I cut the wires of the Fiesta, making sure to keep a good lenght of wire in both ends, the one that stay in the car for the next player and the one that comes with the plug to my explorer....
Then, I already have and adaptor used to not cut the wires on the X, so, I grab the plug, macht the wires, 12v, speakers, ground, amplifier, and all the stuff, and I got a CD player from a friend, in payment to mount his new Pioneer CD player....
Hope this helps...