Complex sentence: As it is facing destruction, "Pegasus" makes a timely arrival destroying a Basestar, Apollo having disobeyed Adama's orders, buying the crew of "Galactica" time to repair their faster-than-light (FTL) drives.
Split into simpler sentences: As it is facing destruction, "Pegasus" makes a timely arrival, destroying a Basestar. Apollo, having disobeyed Adama's orders by bringing Pegasus into the fight, buys the crew of "Galactica" time to repair their faster-than-light (FTL) drives.