Keep fixing it until it's broke. Maybe that plug turned green from the coil that the dealer replaced. If it runs fine drive it.
The coils are easy to replace. Unplug your maf sensor(squeeze bottom of plug and pull down), loosen off the upper hose clamp on the aircleaner(10mm), Remove 3-10mm bolts holding air cleaner, lift on front drivers side corner to remove. Aircleaner has a dowel that sits in a rubber plug on the front drivers corner of valve cover and can sometimes stick in there good. Ignition coils are right on top, 1 10mm bolt holding each one in place. You could have replaced your spark plugs with 2 sockets, a ratchet and an extension. Cobrajet or topfuel did a how-to I believe.
View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)