Honda Accord misfiring?

I have a 2009 Honda Accord that is misfiring. I took it to the mechanic and he explained that oil was leaking into a spark plug. He replaced that plug and the issue came back next day. I got the codes and was recommended to change all spark plugs and the tube/o ring. Will that fix the issue?

Yes - all the tube o-rings. The labor is much more than the part price. Oil leakage in the tubes is a common problem with Honda engines and almost always leads to the sort of symptoms you describe. Check out the video to see how it is done.

Changing the plugs will not solve the problem. It is coming through the piston rings.

It's common that the spark plug tower tubes get oil i them as the motor gets older. The o-rings that seal the tubes harden and leak.
All Honda motors have an issue with the valves getting tight which causes misfires, lack of power, and a poor idle speed.
When the valve cover is taken off to replace the o-rings get the valves adjusted!

Valve cover seal/o-ring should fix it. Just changing the plug is useless if the spark plug well is filling with oil.