timing belt adjustment

We recently had to have the water pump replaced. We were also ADVISED TO HAVE THE TIMING BELT REPLACED. When we got the car back it ran extremely rough in low idle and would shut off unless it was revved. We brought it back and the mechanic agreed it was the timing and said he would adjust it at no charge. he said it was four hours labor to adjust. We got it back and it still is not right. The questions are: 'Does the engine really need to be taken apart just to adjust the timing?' and 'Should we look for another mechanic if this one can't time an engine?'