How many kms are on the engine? If it has high miles, there may be a chance
that you just need a head gasket. The question is, if he was driving the
car at the time with low coolant and the gasket suddenly let go where it was
weak, if there is any damage done to the engine as a result of overheating.
The result could be anything from a cracked block, or warped head or worse.
As far as the timing belt, I know I had to change the timing belt on my
older 1990 1.9L Escort at least every two or three years. It was
recommended to change it every 110,000 kms. The older 1.9L engines are
interference (some people will argue that they are not, I saw for myself
with my Escort when it happened to me). If the belt snaps on the highway or
while the car is being driven, there is a chance of any of the pistons
hitting and damaging the valves, which would cause the pinging noise. But
if you can visually see coolant dripping from the engine, I have my doubts
there is anything wrong with the timing belt. I would however, check the
water pump to make sure it hasn't seized up. Depending on the mileage and
the quality of the pump from when the new one was installed, it may very
well need another one.
The first step is to get it to a shop that you know you can trust. Then,
once you know what is wrong, worry about the repairs.