Complex sentence: Plumeri assumed the post of Chairman & Chief Executive Officer at Willis on October 15,2000, replacing John Reeve, who retired, and becoming the company's first non-British CEO and first non-insurance industry CEO.
Split into simpler sentences: Plumeri assumed the post of Chairman & Chief Executive Officer at Willis on October 15,2000. He replaced John Reeve, who retired, and became the company's first non-British CEO and first non-insurance industry CEO.