Cadillac Catera brake light switch

Brakes problem
Cadillac Catera V6 Wheel Drive Type unknown Automatic 140000 miles

Hi, None of my brake lights will come on. We checked all the fused and changed all the bulbs. All the blinkers, emergency light etc. Come on. Even the dash brake light comes on so in researching the internet I found out it could possibly be the brake light switch. I purchased a new one but there is a plastic bar that keeps me from seeing up in there exactly what I am doing and I don't know what it is attached to. I need a diagram of underneath there if you can get one for me. My email is dsgermick@charter. Net