What Are The Risks Of Mastectomy?

I'm writing about my 95 year-old mother - generally in good health but blind, and recently diagnosed with a large tumor in her left breast. the dr has taken a needle biopsy. he indicated the tumor is likely cancer and does not think it has invaded the lymph nodes at present. he's recommending a mastechtomy. what are the risks of surgery for her? what after-care is required (she's presently living in an assisted living facility)? what should she do? we live in the myrtle beach sc area.