Is the shifter locked in Park? If so, it may have to do with the interlock mechanism. I've included that portion of my '03 service manual. Maybe you can figure out how to disconnect the system.
Another possible cause for the shifter inop. is the plastic rod inside the shifter rod. To verify, simply pull the shifter straight up and the plastic rod is in the center of the tube. Inspect the rod for a break on the lower section to the mechanism.