I've replaced the coil pack and fitted new spark plugs. However, the salesman, while handing me the plugs, accidentally dropped two of them on his table. I remember them dropping from about 2 inches above the table. They were still in their boxes and hit the table horizontally. I carefully inspected them twice before handing the money, and the insulator (both the visible part of the core and the stem) seemed fine with no visible cracks, the gaps were also right, so i bought them.
I've installed them, and after driving around for about 3 days, the car is idling fine and acting like it isn't misfiring under load (previous coils and sparks were causing a minor misfire on the 1st cylinder and this made the car noticeably hesitate under load, even though it still idled fine), both on a cold engine and a hot engine.
Am i worrying for nothing, or would i better change all sparkplugs again?