You need to have the codes pulled 1st. As far as the easiest coil/plug replacement, #s 1-3 are the most difficult and require the upper intake manifold to be removed. #s 4-6 are right in front and are very simple to replace.Did they replace the spark plug at the same time?It may be the plug thats at fault not the coil.One other thing-depending on the mileage-sometimes all thats needed is the coil BOOT not the whole coil assembly.The boot is a fraction of the cost of a new coil. Eventually the rubber boots dry out and lose their insulating capability,resulting in the coil firing thru them onto the cylinder head and not on to the spark plug .This causes the missfire and check engine light.If you drive it too long missfiring it will flood the catalyist( inside the) the cat. converter with fuel and ruin it-very expensive! Take it to a Dealer (Mazda or Ford).Here in the North East Ive heard the Ford dealers are less expensive than Mazda.If its a missfire code have them replace the faulty coil (if needed) all the plugs and all the boots.Worn out boots should have a burn mark where the coil electricity has been shooting thru them. Good luck and please let me know how it turns out or if you need any further assistance!

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