If it's like my '89, you have to replace the whole assembly. Inside the hatch behind the tail light there's a knurled knob. Remove it and push on the stud and the tail light pivots out on its far outboard end and is removed from outside the car. There's a plug that disconnects and you can carry it over to the bench. Bulbs are replaced from the rear of the assembly, where there is a wiring harness.