If your old one is not torn, they can look terrible and still be salvageable. Mine had a brown brittle coating with lots of overspray from a cheap paint job, but it wasn't torn or cracked. It took a flat screwdriver blade to clean the grooves, lots of rags, and a quart of lacquer thinner, but by the time I finished it looked like a new part, and my clothes and gloves looked like I had been playing in tar. The guy who installed the windshield thought the gasket was new, and three years later it still looks good.