For a unique visit with one of America 's greatest storytellers, watch a ''Conversation with Jean Shepherd" on ''New Jersey News: Special Report'' Tuesday, Jan. 11 at 9:30 P.M. on New Jersey Public Television channel 50. NJPTV entertainnient critic Ellen Wexler will conduct the half-hour interview with America's modern-day Mark Twain as he expounds on such topics as politics, Jimmy Carter and the new year, his best-selling novels, the Garden State and his ideas on what he calls "the watchers and the doers - the winners and the losers."