Amtrak is trying to win over some repeat customers. So the company last week announced a new satisfaction guarantee to change its unfriendly image. The new guarantee applies to all gripes, with the notable exception of late and broken-down trains. Customers who have any other kind of complaint can call Amtrak headquarters to get a voucher for a free ride. The company hopes to get at least 1% of its first-time customers to return, meaning another $13 million in annual revenue. Congress has ordered Amtrak to be self-sufficient by 2003.