2003 V8 4.7 Engine Code & Blinking Check Engine Light

I recently installed a used motor and the check engine light is blinking which I know is not good. Code reader keeps jumping back n forth from Misfire Cyl 6, then goes to Misfire Cyl 2,4,6,8. Runs very rough and is very very rich in fuel dept. I was told to maybe clear my ECM and possibly install new firmware version.
My question is this maybe my mechanic and I can attempt or is it a Toyota dealership thing?
Thanks for any and all help

 

Welcome

 

Welcome from Arizona!

 

Not all code readers are equal capability. The expensive ones , usually owned by professional auto electro-mechanics , give more information on deeper levels of your on board computer OBD2.
And understanding that information takes knowledge and experience.
See if you can get references for an independent top notch auto electrical specialist: try asking around at local car shows, ask at independent shops. Forget dealers unless you have a relative working there. My experience is they have no diagnostic skills. They just replace parts hoping the parts fix your complaint.