Complex sentence: He spent his final days on earth preparing those around him to be able to cope with his death, until he had finally succumb to his illness on December 12,2002, just 3 days before his 45th Birthday.
Split into simpler sentences: He spent his final days on earth preparing those around him to be able to cope with his death. He died on December 12,2002, just 3 days before his 45th Birthday.