How to change a mustang brake light?

I have a 2000 mustang that I can%26#039;t change the brake light. I removed the nuts from the 4 screws and I can see it get loose but the screw in the middle seems to have some type of metal ring that I can get off.. Need help ASAP|||Is it a round flat cotter pin? Try pushing it off using a flat nose screwdriver.|||In a 2000 Mustang, the tail light assembly has to be removed from the car to replace the bulb. It is very easy. There should be 3 long brass colored threaded rods with, I believe 7/16 nuts on them. Remove all the nuts and push it straight back, away from the tail light panel. Then just turn the socket and it will be able to be removed from the assembly. Be careful not to handle the bulb with your bare hands as the oils in your skin will shorten the bulbs life.|||Might take a little more pulling pressure. The washers are water seals and they stick pretty good to the metal after a few years. Take a straight screwdriver and gently pry them back. Wiggle the housing up and down and they should start to break loose. Hope this helps.