If you haven’t yet you still got to figure out how you get the old oil out, what you put it in to (got to have some sturdy containers because it’s going to be hot and messy and you have to transport it) what tool you need for the filter, what to put under the filter to catch the drips, what you gonna do with all the rags and paper towels you use and how you going to get oil from a gallon container into the engine. (I have a funnel or you can make one out of a plastic soda bottle)
I happen to use Rotella but don’t believe it matters as long as it is good oil, and staying with one type avoids any possibility of incompatibility. I also spring for genuine Yanmar filters. You decide if a $20,000 engine is worth it.