Faulty gas gauge

2001 chevy silverado ext. cab LS 5.3 V8 195,000 miles. For about four years the gas gauge has had a mind of its own. At full, the gauge wont start working untill i've burned about a 1/4 tank and after that it alternates between empty and the amount I have left. Other than that the truck is in perfect running condition, no check engine lights on dash. Mechanic shop tried to entice me in to $800 in repairs 4 years ago, said I needed a new fuel pump and some other preventive maintenance or else I might wind up stranded. 80,000 miles later I guess prooved them wrong. Any ideas?