Complex sentence: In 2007, Mayor George Whitehurst, who had been mayor for nearly 20 years, resigned, leading to the inauguration of David Cadle, who had just retired from directorship of the Crestview High School (Florida) band, The Big Red Machine.
Split into simpler sentences: In 2007, Mayor George Whitehurst, who had been mayor for nearly 20 years, resigned, leading to the inauguration of David Cadle. Cadle had recently retired as the long-time director of the Crestview High School (Florida) band, The Big Red Machine.