I took both the one day seminar and the three day shop course a few years ago. The one day is excellent for the new boat owner who wants to understand how the engine works and to be able to diagnose simple problems. Good info on the care and feeding of a diesel engine. If you are new to boating it is really great. For a long time boat owner, not so much.
The three day shop course is excellent for anyone interested in working on their own engine. After attending the course, I felt that I could accomplish any normal repair using the manual as a cookbook. There is nothing like working on your engine model on a test stand in a shop with an instructor to give you confidence.
You change all fluids, belts, filters, dismantle and reassemble pumps, remove and replace injectors, adjust valves, torque the head and dismantle and reassemble the heat exchanger.
I enjoyed it and learned a lot.