After three decades of working behind the scenes for the stars — including Barbra Streisand, Bette Midler, Ben Affleck, Leonardo DiCaprio, Jon Bon Jovi, Tyler Perry, as well as for many prominent New York Democrats — public-relations guru Ken Sunshine is finally stepping into the spot light himself. Sunshine is set to join Jimmy Nederlander and Midler as a producer of the much buzzed-about musical “Priscilla: Queen of the Desert,” which opens today at The Palace on Broadway.