First find the underlying problem that caused it to go bad. They never go bad on their own. THEN start getting prices for a replacement, but only if you need it. Read this on why they go bad.

http://ricksfreeautorepairadvice.com/cat...

Depends on which vehicle.

I do disagree with Been There though. I had a '97 Dodge that needed a new catalyst and I bought a universal converter. I had to install a flex pipe with it but it worked and passed emissions testing after.

depends very much on car. often cheaper online than dealers.

Not only depends on what car, but which converter (some have only one; some as many as 4) and where you are. If you are in California and possibly some others you have to use a CARB approved part, which can be much more expensive than an aftermarket converter.

By all means, get a second opinion. Converters are suspected of being clogged far more often than they actually are.

cars older than '94 are cheap, as they can use a universal, fit-all unit.

After '94, you have to use the unit designated for your specific car and it's anywhere from 600- 1500 or so.

Go to a muffler shop. NOT a dealer.