mml47

About a year ago I had the water pump and the intake gasket replaced among other things because one thing led to another. The truck had been running perfectly until just a few days ago when it started to sputter at idle and make a loud pinging noise when accelerating and decelerating. The check engine light cameon today and started to flash constantly. The temperature gaugeremains fine though it may be stuck, but I dont think so. The shop says thehead gasket is shot and they want to pull the cyclinder heads and replace everything for $1900or recommend getting a new engine. Anyone agree with this or may know what the problem is and the price I should pay to solve this problem. Much thanks appreciated.