Richard, seriously? You bought a used car and didn't think you were taking a chance that you might have to put some $$ into it? You didn't mention how used the car was. What year/model? Also, why would the dealership be at fault if YOU had to replace the windshield at some point in time. Did they throw a rock at your car?
I don't know about the warranty, though. That smells fishy, but most extended warranties are not worth the paper they are written on.