http://www.rockauto.com/ref/ACDelco/....html?C883.jpg
This should be a similar picture of your switch. It should be up under the dash at or near the pivot point for the brake pedal arm. Have someone watch the brake lights while you press the plunger on the switch and see if they work if so, if they do the distance between the switch plunger and brake arm need to be adjusted.
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There may also be a fuse for the brake lights, but I am not sure where the fuse box would be for your year vehicle.