1998 Plymouth Voyager Bucking upon acceleration

Hi, recently started to experience a bucking sensation when accelerating that comes and goes. Sometimes the "service engine soon" light starts flashing 5 times. Then it came on permenantly and brought the car in for service. They said that cyclindar #2 was misfiring and they said that the spark plug gap was off and they fixed it. The car drove fine for a week and now it's starting to do it all over again. Would a tune-up with new spark plugs likely solve the problem? How often should this vehicle need a tune-up?