Sgt411,the lamp assembly can be ordered as a separate part from the mirror.I am sorry I don't have the part number,I did not get an invoice ,since this was a warranty repair.
When the part came in I took the X to the body shop and watched the boys put it in.They had not replaced one before,I told them mine could be their beta vehicle.The mirror has to be disassemled .The mirror,not the housing,is secured by three small clips that slide back.The mirror is tilted from one side to the other to slide the clips back. Once they are slid back.one on each side and one on top,the mirror comes out of the housing.Any wires on the mirror can be pulled off at this time.There is one screw holding the lamp assembly in place,remove it and disconnect the two wires and the assembly snaps out of the mirror.It took about 45 min.I am sure the next ones will be faster.
YOur dealer needs to look in parts manual again.I don,t think Ford would approve of replacing ahigh dollar mirror over a $78.00 lamp.