KINGSPORT — The first show of Kingsport Theatre Guild’s 2019-2020 season will open Friday night, and tickets are still available. KTG will stage “West Side Story,” a modernized rendition of “Romeo and Juliet,” this weekend and next at the Renaissance Center mainstage. Tina Radtke, executive director of KTG, said the show is unique in that the cast features several families, and it will include a full orchestra. “To my knowledge, KTG has never done this show before,” Radtke said.