The third and final seminar of the National Museum of Racing's "Guests in the Gallery" program will be held on Aug. 21 at 11:00 a.m., in the Hall of Fame Theater. Participants expected to attend include Laura Tilbury, licensed Message Therapist and Licensed Veterinary Technician; Don Baxter, farrier and veterinary assistant; and Veterinarian Dr. Greg Bennent. "Guests in the Gallery" is designed to give the public the opportunity to meet individuals who are closely associated with the sport of racing. The program is free with paid admission to the Museum. ...The National Museum of Racing and Hall of Fame will also host a sneak preview of Seabiscuit, an American Experience documentary for PBS, on Aug. 21 and Aug. 22. A sports hero of the 1930s Depression era, Seabiscuit's rags-to-riches tale is now brought to PBS by award-winning filmmaker Stephen Ives, and will be broadcast nationally in the spring of 2003 as part of American Experience, PBS's acclaimed history series from WGBH Boston. The premiere celebration on Wednesday will begin at 6 p.m. with cocktails, music, and a buffet dinner followed by the movie at 8:00 p.m. Filmmaker Stephen Ives will be on hand to introduce the movie and answer questions. For tickets, priced at $75 each, please call 518-584-0400 extension 135. Fans who miss the evening premiere will have another chance at a sneak preview on Thursday at 10:30 a.m. and 2:30 p.m. Tickets are available the day of the show with museum admission. The museum opens at 9:00 a.m. Seating is limited.