We got our oil changed a fluids checked @ wal-mart & we returned home & shut the car off. 20 mins. later when we tried to start it back up, it made a metal grinding noise in the engine every 4 seconds for 1 minute or so & shut off. charged the battery and it would turnover but wouldn't run. We asked a mechanic to take a look at it and he said it was the timing belt, he replace the part and now says it wont start. he thinks its the cylinder head. he said he thinks we probably messed it up when we were trying to start it? please help asap...its winter and no vehicle, i have a 5 month old baby girl...