Robert, this is from the FAQ list, available from the top line of this forum. There may be more in there. This is probably the best guide available
Ian F

Center Stop Lamp.

Sedan/Saloon. [Inquiry] The high-level brake light (the one that sits in the rear window) is dead in my car. I can't seem to figure out how to access the bulbs. The manual has an unhelpful picture of a screwdriver underneath the cover with the description: depress the catch with a screwdriver. I can't seem to find this catch.

[Response: Bob] For 740/760 sedan cars, there should be a hole in the bottom side of the cover. The catch is tricky to find. Keep probing and push up with a screwdriver while wiggling the cover. For 940/960 sedan cars, try to spread the stop lamp cover outward to release the hooked catches on the sides that hold it to the lens assembly, which in turn is secured to the chassis mount screwed to the package shelf. Once the cover is off, reach up beneath the lens assembly and locate the hooked tab on the chassis mount below the center bottom of the lens assembly: depress this tab and pull off the lens. Be careful: the plastic can embrittle from UV exposure.