Hey, Alex. You actually have 6 coils and 12 spark plugs on your engine.

Sounds to me like your mechanic is shotgunning it.

Plugs are pretty easy, if you have the tricky wrench to get the boots off., about $25 on ebay. Check the wires for resistance while you're swapping the plugs and replace any that test more than 25 or 26K.

Coils rarely fail on these engines, and when they do it's not all at once. Since all of your misfires are on one bank, it's more likely to be a vacuum leak, a bad cat or a flagging O2 sensor that is triggering the codes. Cats are problematic on your model anyway, in case you didn't know.

But I'd start easy and inexpensive. Change the plugs and test the wires while there (note that there is an a and b plug for each cylinder, that correlates to the a and b on each coil, be sure to match them up, no anti-seize, Bosch 7422 IIRC). Check for vacuum leaks (everywhere) while you've got stuff pulled apart, and replace the breather hoses and reseal the covers (common leak points), too. Take your time and be thorough and that will cost you most of a day, but it's much more satisfying (and cheaper) than shotgunning it.