Chevrolet: 2001 Cavalier engine problem, motor job, valve spring

Question
I do not, he had it towed home because the noise was so bad he was afraid he would ruin something worse if he drove it.  I have not heard the noise, I am just concerned that it could cost several thousands to fix it and not sure what to do.  He called a dealer and they said have it towed to them and they would give us a price.  He doesn't have a lot of money, so I was hoping to get an idea what type of cost I could expect to have if he really did ruined it.
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Followup To

Question -
Son's car, thinks it was out of oil and he needs a new engine or rebuilt one, it is making a clanking metal on metal sound.  where can I get an idea how much it will cost and whether to go with new or rebuilt?

Answer -
Sally;
 Hi  just go on line and look up rebuilt engines you will find a bunch of them.   ok >> how do you know it is blown ?

Answer
SALLY
 Hi- well first off-STAY AWAY from DEALERS- they will rob you blind , and with a motor job WOW.
If you must I would see if you can have some mech. look at it to give you a idea of what is wrong. As far as noise - it could be something that is not too bad- IE the water pump can make noises. or a broken valve spring,etc. so I would not get upset yet. It could be something that might only cost a few  hundret. so do not get taken. ok