The driver's /user's manual does mention it for a sedan model but not for a station wagon ( instead, the manual says 'refer to qualified technicians'). I had a Chilton's repair manual for 86-92 Ford but it has only very brief description.
The problem is actually how to remove the rear lamp assembly. I have removed the (two) philips screws on the plastic assembly but the assembly would not come off -- too little force? well it may break if I applied too much. It seems there is three screw somewhere from 'inside' but I just could not find it either on the assy. or inside the spare tire compartment.