How can osteosarcoma affect a person?

In many ways. Osteosarcoma is a primary cancer of the bone. It occurs primarily in the long bones and is usually associated with pain that ocurrs after a seemingly simple injury or pain that does not seem to subside after a normal period of time. A simple xray will dtect abnormal bone formation. A biopsy is needed to confirm and then surgery to remove it and possibly chemotherapy.
Depends. "patients with localized osteosarcoma undergoing surgery and chemotherapy have a 5-year overall survival (os) of 65% to 70%." see: http://www.Webmd.Com/cancer/tc/ncicdr0000062698-localized-osteosarcomamalignant-fibrous-histiocytoma-of-bone.