Catalytic Converter problem

Hi
I have a 2001 Toyota corolla with 95K miles on it. Of late,I have the check engine light appearing and upon taking to a mechanic, they say the cats has gone bad and need to replace it. The OEM costs around $1100. I was able to find an after market one for $510. Is is worth going for the after market cat? quite confused if I need to do the reparis or just sell the car and go for a new one. I just changed my tires recently (all 4 of them) and when I checked with carmax, I was offered $3500 for it (as it had an accident).
Gurus, any advise on this?

Thanks.

Need more info:

The code

If you do not know, have the diagnostic code read at Autozone for free.

Doubt if it is the converter, unless your having severe drivability problems [with the low mialage you've indicated]

SO get the code before oyu pay for anything

Need more info:

The code

If you do not know, have the diagnostic code read at Autozone for free.

Doubt if it is the converter, unless your having severe drivability problems [with the low mialage you've indicated]

SO get the code before oyu pay for anything

The code is 420. However, I don't see any difference in the mileage I gain from my car or do I have any drivability issues. Not sure what to do!

If you vehicle does not have to undergo emmisions testing as part of your local safety inspection process, and there are no performance problems I wouldn't worry too much. If, however, the performance of your vehicle begins to degrade you may need this addressed. It may, or may not need replacement. The cost of the converter may be warrantied by the automaker. Someone mentioned 8 years or 80,000 miles on toyota emmision parts. Do some research. Don't ask the dealer directly...they'll say not covered

from obd2 website::

A code P0420 may mean that one or more of the following has happened:

Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged exhaust manifold / catalytic converter / exhaust pipe
Retarded spark timing

Possible SolutionsThe simplest thing to do is to reset the code and see if it comes back.

Next step is to measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). The voltage should be low and steady (~200mV, depends on the vehicle). If the voltage varies (e.g. 100mV to 600mV) then it's time to replace the catalytic converter. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.