How risky is a hernia operation for a man in his late 70s?

Fitness?: Depends on how vigorous a man he is. Does he walk independently or is he bed-bound. Can he walk up stairs? Is he on 1 medication or 25 medications? Smoker? Obese? Exact age is less important than health. Some 78 years olds are medically much younger than some 50 year olds talk to your medical doctor. Generally these are not high risk surgeries.

Depends: Chronological age is only a single factor. It also depends on the overall health, previous operations and type and size of the hernia. In general, hernias are repaired to resolve a problem, prevent a problem or both. Use your common sense, and consider the risks and benefits if all options including observation. Good luck!