Though each of them took place more than 25 years ago - before the rise digital television, Flip camcorders or the great Thierry Henry controversy that's still dominating international sports headlines - the two most important on-field events in my life require no instant replay.   I remember them perfectly well.   They involve two of the times that my dad, straight after his work at the auto shop and still wearing his grease-encrusted "Dinan Auto" work shirt and pants, rushed onto a playing field in our quiet Connecticut town to defend the honor of one of his sons.   The first time it was my older brother Terry's. The 10-year-old had become embroiled in an argument near second base at Gamble Field, one of two little league diamonds at Mead Park in New Canaan, Conn. I was sitting among the spectators in the little aluminum grandstands - among the well-to-do men in polo shirts, khakis and loafers and their long-haired wives, varicose vein embolisms giving courage to short shorts that, the way they were crossed on the open grandstands, led to exciting, confused thoughts in my own 8-year-old mind.   Among them and my dad. Marlboro Red dangling from his face (he would switch to Marlboro Lights in my teenage years, and finally, after re-marrying a Swedish woman whose idea of lunch was cucumber slices and yogurt, to a pipe), dad stood a little apart from the grandstand crowd, gazing intently at my brother, a natural shortstop who early in his career had a habit of "pushing" rather than throwing the ball to first base.   At some point in the game it happened - Rob Ardigo rounded second base and collided with my brother somewhere between second a third. A fight ensued, and one of the coaches emerged from the bench to where the two boys stood tussling.