Power Steering Failed problems of the 2004 Nissan Frontier

Powering steering box failure on a 2004 Nissan Frontier. My vehicle has only 49,000 miles on it and was purchased new. Two mechanics, one Nissan and one an independent mechanic, identified the steering box as the culprit for the difficult steering in the vehicle. Both said it should not fail. The Nissan mechanic went on to say that he had only seen one fail in his ten years as a mechanic, and that involved a vehicle that was in a severe accident. The failure prevents me from steering and at times takes two hands to steer. The mechanics state that the only repair is to replace the part. Nissan refuses to assist in the costs of those repairs.