What are the Parts and Labor cost for replacing the Gasket-Rocker cover, a new Gasket-Manifold and a Gasket Adapter-Fuel injection throttle, along with a Cover Assy-Valve Rocker?

I needed a tune up. The Nissan Dealership Mechanic said along with replacing the spark plugs, I need a new Gasket-Rocker cover, a new Gasket-Manifold and a Gasket Adapter-Fuel injection throttle, along with a Cover Assy-Valve Rocker, because there is oil coming from both ends of the engine. He said it will take 2 hours. I'm being charged with $334 in parts and $400 for Labor. That's $200 an hour. Are all the parts needed and is $400 too much?
Thank you