Check Engine Light: P420

[AzSubaru-RepairRipOff?]

Subaru Forester 2000. So the check engine light comes and goes. Advertised repair shop says replace entire converter ($1300) cause it's not the sensors. So I wait for the light to go out and take it to state emissions and pass. I'm thinking repair shops desperate for money and it is one of 2 sensors. Any thoughts on how to proceed or am I an over paranoid senior?

 

[AzSubaru-RepairRipOff?]

New ownership and staff fixed other issues of fault by previous owner and staff. Still have no "check engine" lights for P420 emissions. Amazing how original problem disappeared. Will have manual emissions check done next.