AJOR LEAGUE BASEBALL HEROES at Shea Stadium cross paths with immigrants on their way to work in this largely industrial section of Flushing, Queens. During New York Mets games, the subway station buckles under a rush only seen during baseball season. When the stadium is closed, the neighborhood is quiet except for the few hundred immigrants changing tire rims and mufflers at more than 150 auto-wrecking shops. In the warm days of spring, parents, schoolchildren, couples and others from around Queens arrive by subway to play along the water at the Flushing Meadows-Corona Park, formerly the site of two World's Fairs. Willets Point was once home to the 77th U.S. Army Reserve Command, where soldiers protected New York's harbors. Today, immigrants work around-the-clock to power the auto-parts bazaar that Willets Point has become.