Complex sentence: Instead of working, she spent the first six months of 1961 preoccupied by health problems, undergoing surgery for her endometriosis and a cholecystectomy, and spending four weeks in hospital care--including a brief stint in a mental ward--for depression.
Split into simpler sentences: Instead of working, she spent the first six months of 1961 preoccupied by health problems. Monroe underwent surgery for her endometriosis, had a cholecystectomy, and spent four weeks in hospital care--including a brief stint in a mental ward--for depression.