Manhattan, N.Y. - Dave Esposito, one of the finest wrestlers in Lehigh's illustrious mat history, has been named an assistant coach at Columbia.  Esposito, 24, will serve as the first assistant to Columbia's third-year head coach, Brendan Buckley. He succeeds John Pozniak.     The addition of Esposito gives the Lions one of the most talented coaching staffs in the nation. All four Columbia coaches -- Buckley, Esposito, graduate   assistant Yero Washington, and volunteer assistant Karl Roesler -- were NCAA All-Americans.     "I'm very happy that Dave has chosen to coach at Columbia," Buckley said. "He was an outstanding wrestler at Lehigh. He also was a superb student, and   is at home both on the mat and in the classroom.  "Dave will provide solid coaching on the mat, but should be equally valuable in recruiting, with his knowledge of scholastic wrestling in New Jersey and Pennsylvania, two states where we concentrate much of our recruiting effort."     Esposito was one of only 12 two-time All-Americans at Lehigh. Wrestling at 149 pounds, he finished second in the 2001 NCAA Championships and third in the 2000 NCAA's. He won the EIWA Championships both seasons, and was voted Outstanding Wrestler of the 2001 Easterns. He also qualified for the 1998   NCAA's, winning two of four bouts.     His finest year was his senior season of 2000-01. In addition to the NCAA and EIWA honors, he was runner-up in the Midlands and the Las Vegas Invitational, going 35-4 overall. He was chosen Lehigh's Most Valuable Wrestler (for the second time) and Senior Male Athlete of the Year. His 105 career victories placed him fifth on the Mountain Hawks' all-time list.     A native of Matawan, N.J., Esposito was a three-time New Jersey state placewinner for John F. Kennedy Memorial High, finishing third twice and second once. He was graduated from Lehigh in 2001 as a Dean's List student in marketing. Since graduation, he has continued to wrestle both nationally and internationally, and coached at The Edge, the New Jersey wrestling club. Both Erik Norgaard, who was 18-7 as a Columbia sophomore last season, and hails from Leonia, N.J., and Devin Mesanko, a key Lion recruit from Toms River, N.J., are products of The Edge.