what type of catlic converter will I need to get I want to buy it myself on 2003 Chevrolet Venture

I replace the 2 sensors but the engine light is still on so I want to replace the cat. conv. so what type should I buy because if I let the mech. do it I know I will be overcharged so I want to buy it and take it with me to the mach.

Asked by for the 2003 Chevrolet Venture
Nobody else has said anything, so we make our living on parts and labor and maybe some charge too much, but to help you save money is fine, and I think you need to research this for your self. Not trying to be rude just stating the facts.
I'm not trying to do it myself I want to know what type of converter I will need to buy my venture is 6cly I'm not sure the engine size but it is a extended body van I looked at the cyl.conv. but I do not know which one to buy ?
The front one
what do you mean, do I get it with the pipe connected or just the converter, I see there are different types?
It can be welded in.
1 more answer
Are you saving any money by changing parts without the problem being diagnosed? In NY you need a CARB compliant converter.