Compiled By John Teresko Worrying about parts for your 1955 Mercedes-Benz 300 SL Gullwing? Relax. You and the other owners of vintage Mercedes models (20 years or older) have a "Christmas present" from Mercedes-Benz USA, Montvale, N.J. For spare-parts information remember this toll-free phone number: 1-866 MBCLASSSIC (622-5277). Classic-car specialists armed with a complete set of technical data are ready to help between the hours of 9:00 a.m. and 5:00 p.m. EST, Monday through Friday. Callers with their car's chassis number (VIN) at hand can determine the genuine Mercedes-Benz replacement part and its part number, check availability and price, and get the phone number of the nearest part department to place an order and take delivery. Inquiries also can be made via e-mail to [email protected]. If you need restoration rather than just parts, remember that in 1993 the company opened its Class Care Center in Fellbach, Germany. A similar facility is being planned for the U.S.