@ledhed75, just because a mechanic gives a price it does not mean they are ripping you off. It is just what a mechanic has access to and trusts for parts. Also labor rates of mechanics are far greater than muffler shops.
Converters are something that can be done at muffler shops just a big question on longevity of a generic vs OEM equivalent.
If the cat is failed but does not hurt vehicle performance, you could drive it as is. But you would have a cel and probably have issues with yearly vehicle inspections and licensing issues. If the tech can verify that the car is running ok and the only issue is a failed cat than you can decide what to do.