2001 Honda Civic Burnt Exhause Valves

2001 Honda Civic Sedan with 135,000 miles. Finally brought car in to a mechanic for an engine light that was on for almost a year. Mechanic tells me I have 3 holes. Computer reads out multiple codes P0301, etc.. After full diagnosis, mechanic claims I have burnt exhaust valves. He estimates approximately $1600-1700 to fix. I tried looking online, but did not find any stories similar to my situation. Is the mechanic right with his approximate? Or are there other, cheaper way to resolve my "diagnosis?"