Did you also find the catalog of part numbers? I find that an invaluable companion to the shop manual.
And once you have a part number, check it out on the TOAD site
http://shop.toadmarinesupply.com/marine_diesel_direct/Yanmar/ to see if it has been superseded with a new part number (and you can see the price).
I can't remember where I found a link to the part number catalog - but it's from a Dutch company (the catalog is in English). There were separate pdf's for 1GM10, 2GM20 and 3GM30. Each covered both raw and fresh water configurations as well as all the various transmissions (even had my V drive). I have the 3GM30 is anyone needs it.
Chris