One of the greatest sports figures of all time salutes his heroes and takes us inside the game as few others can.      No one has been as close to the game as Wayne Gretzky. When he first laced up skates in the NHL, he changed the league. And by the time he had hung up his skates, he had re-written the record book.      There can be no doubt what he means to the game. What we haven't seen is what the game means to him.     For the first time, Wayne Gretzky will tell us about