High end Marina''s up in the Northeast get about $80 an hour for diesel work. There are very good independant deisel mechanics (but a little hard to find) that charge closer to $50 an hour. It really shouldn''t take much more than 1 1/2 to 2 hours max to do all the things you listed. I think someone who worked fast & knew what he was doing could do it under an hour.
Time to do work items.
*Heat engine (to loosen sediment & heat oil for removal)-- 5-10 Minutes
* Change Oil and filter -- 10 minutes total using an electric oil-removal pump
* Change transmission fluid -- 10 minutes total using a oil-removal pump
* Replace impeller -- 5-10 minutes depending on position
* Change Fuel Filter and re-bleed engine fuel lines -- 10 to 20 minutes (depending on engine)
* Clean raw water strainer - 2 minutes
* Change heat exchanger zincs- 5 minutes
* Time to remove engine access and replace with Clean up -- 15 minutes
Cost for parts (varies greatly- this is ballpark price)-- Oil $9 - Fuel Filter $15 - Oil Filter - $12 - Impeller - $20 -- Zinc -$5
I think it sounds high, but not out his mind high........But I still think its too much, that is why I do most of my own work.