Car was suddenly sputtering and idling rough. Changed spark plugs and a couple of ignition coils in response to misfire error codes. No change. Learned there is no spark on 5th cylinder. My local repair guy says he thinks it's 'the computer.' Any thoughts???

 

I'd inspect the wire harness before blaming the computer. You can check both at the coil side as well as consider removing the ECU and cleaning the contacts.