Another former assistant to Britney Spears was served a subpoena from Kevin Federline's lawyer last night to testify in her ex-boss's custody trial. Shannon Funk arrived at the Long Island airport to a waiting throng of paparazzi and the legal papers.According to the New York Daily News, Spears is getting ready for a surprise performance at the MTV Video Music Awards with new manager Jeff Kwatinez. Her record label is reportedly "worried any missteps (or a no-show) could hurt her comeback."