my 1998 nissan sentra head gsaket is blown how much will it cost to repair it on 1998 Nissan Sentra

the car was overheated i changed water pump, thermostat and radiator cap but it still overheats mechanic is charging me $900 to rebuild engine head gasket and his labor

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at least 1400.00 parts and labor not incl cause or cracked cyl head