The wait is over. Let the rejoicing begin. Three years after the project was first announced (Daily Variety, May 23, 1994), Barney will officially trumpet his motion picture debut on Friday morning.The lovable-to-some purple dinosaur, clad in Hawaiian shirt and sunglasses, will emerge from a chauffeur-driven Cadillac at the Beverly Hills Hotel. He’ll greet the press, hand out T-shirts and plush toys, and offer his philosophy of life. Oh, yeah, he’ll also plug his film. “Barney’s Great Adventure,” with a $15 million budget, will begin lensing next month, with Steve Gomer directing a script by Steve White. Producing the pic will be creator Sheryl Leach and Dennis DeShazer. The exec producer is Ben Myron and co-producer is Jim Rowley. “Adventure,” which is scheduled for a spring 1998 release, will give Polygram high-profile entree into kids fare for its new distribution arm. The project was stuck in the tar pits of development for years. On Friday, the dancing dino will attempt to remind everyone that nice guys finish first.