Complex sentence: His last role, shortly before his death, was in an episode of Gunsmoke in 1963, thus bringing to a close a career of an astonishing 51 years in film, with a total of 607 films and television episodes to his credit.
Split into simpler sentences: His last role, was in an episode of Gunsmoke in 1963. His career spanned 51 years, with a total of 607 films and television episodes to his credit.