Replacing third brake light bulb, 1995 Lexus LS400
 

Maybe someone here can steer me the right way here. I need to replace one of the brake light bulbs up on the rear shelf on my mom's 1995 Lexus LS400. The manual states in so many words to take your car to the dealer if a bulb goes out. There's no stinkin' way I'm paying the stealership $50 to replace a .60¢ light bulb. So, how do I get the cover off to DIY and save $50? I've never had to deal with replacing a bulb on a third brake light fixture before.
-Joe