What kind of and intensity of exercise can I do 6-7 weeks post op from a radical hysterectomy to improve abdominal musculature and reduce tummy overha?

Core muscles buildup. If surgery is recent then allow the swelling to settle. After a few weeks, your surgeon will allow you to start diet and exercise. Start with aerobic workouts like treadmill or elliptical. At the gym, there will specific machines which support your back while you exercise your core muscles. If the pannus does not settle then you may need a tummy tuck. See a plastic surgeon to discuss your options.
Slow and easy... You want to be very careful to follow your surgeon's lead here. Getting active is an admirable goal, and there's no reason why you shouldn't shoot for a full return of function, or even improvement. But advancing too quickly may lead to muscle strain and set you way back. Start with walking. Strengh exercises might well be guided by a physical therapist, at least at first. Good luck. Lgromko, md.