95 C280, questions about brake booster
 

Lastnight my wife called saying she had no brakes. When I got there the brake pedal was hard as a rock and the car was running really ruff. I also noticed that it was making a hissing noise that was coming from where the booster or master cylinder is.
Is this a sign of my brake booster gone bad?

If the large plastic vacuum line is connected to the booster then YES.