Timing belt on 2000 Saturn

My mechanic told me the ball bearings for the tension arm shattered, and one of the pistons is out of line. He thinks that this piston may be damaged.
what is the likely hood that the piston is damaged? He is changing the timing belt and tension arm, but he told me he can't tell if the piston is damaged until he changes everything and puts it back together. The car starts, but makes a lot of noise due to the bearings rattling around. The timing belt did not break, but teeth were broken by the bearings. I don't want to spend a lot of money if the piston is damaged because the car is not worth the repair.