Misfire CAN waste your catalyst eventually. But, the #1 reason for the check engine light is loose gas cap.
But check those bad coils - misfires can blow out your catalyst, and that's NOT cheap, especially since in many states, you need it to pass the state inspection.
Oh yeah, I'd look long and hard elsewhere before popping for an 02 sensor, unless it was cheap. They're SUPPOSED to last the life of a car.
Oh yes, and if it's recent enough, it may be warrenty covered - there's a special warrenty for emissions guts.
As for flashing the ECU? One better: Recent automatic transmission Hondas need the whole ECU replaced if you change the 3rd gear clutch. Guess what pops a lot on recent Hondas...
