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To replace the timing chain cover, the engine does not have to be removed. It can be done with the engine still in the vehicle.
The labor is 5.5 hours.
You will need a timing cover gasket that is $9 and it would be best to replace the water pump while you are there. It is $132. No extra labor.
Their estimate is too high.
It is just a gasket failure. have the timing cover gasket replaced. You can call around and get different prices from other repair shops for the repair.
The labor is only about $500. the parts are $145. That is short of $1200.