Damage is only done if the motor is an "interference" design. I.E. The valves and the pistons overlap in the same place, only kept from colliding by the timing chain.
When the timing chain breaks on a interference design, valves and pistons smash together. If it's not an interference design, the pistons and valves won't come into contact if the timing chain breaks, so odds are no internal damage done.
Replacing a timing chain would not have anything to do with compression at the cylinders so I don't believe the mechanic is at fault here. I would suspect that the timing chain has indeed caused internal damage to your engine.
You can confirm that your engine is an interference design by contacting your local dealer and giving them your VIN and engine size. If it is interference, you will more than likely need major repairs.
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Wednesday, January 21st, 2009 AT 11:57 PM