If it is the same as my 420 sel,it is in three parts.1.Remove back part by CAREFULLY prying the tabs on each side out.This is the light bulb housing.2.You will see two black pieces of plastic spring loaded parts that hold the reflector housing up against the rear window.Hold housing with both hands applying lite preasure down on each spring loaded part and CAREFULLY pull the housing streight back away from back window. NOTE: if you break the black parts, you are scr------d.You will have to buy the intire assy. Don't ask me how i know. All of the plastic parts on these old cars are very brittle.