When your old Vivatar point-and-shoot broke, you just threw it out. But now that you've upgraded to an envy-inducing Leica, what do you do if it stops working? The photogs we asked, including such notables as Danny Clinch and Michael Lavine (who, individually, have shot for such publications as Rolling Stone, Esquire, and this one), pointed to Professional Camera Repair Service (37 West 47th Street; 382-0550). The 53-year-old shop will furnish you with a free written estimate (important, since rates begin at $75 an hour, plus parts), and the shop's very particular fans cite its thoroughness. "We don't want you back," says co-owner Rick Rankin. "Not with the same problem."