Three strikes and you are out - add a losing record, 56 errors, a bunch of balks and a number of questionable plays, and it's inevitable that the New York Mets would be offered help.
   One compelling offer comes from some seasoned Long Island baseball veterans, who are joining to produce a video on the fundamentals of baseball to help their hapless metropolitan team. With a cumulative total of more than 1,400 years' experience, the Bristal All-Stars, a Long Island senior softball team, will work on basics the Mets have at times had trouble mastering, from touching the bases to catching fly balls, Wednesday morning at Baldwin Park. Then they'll package the highlights and present them to the Mets.
   The idea came during senior softball games where players groused over how poorly the Mets played the previous night, said Howard Cannon, a spokesman for the assisted living company that funds the league and participating teams.