I have a Yanmar 2GMF also and yes, it uses the same type of oil that the engine uses. (Not all Yanmar engines do ) There is a separate oil dipstick on the transmission. We use Shell Rotella T as recomended by the Mack Boring class I took. In our area the best place to find the Shell Rotella oil is at truck stops that service diesel trucks.
The one-day basic diesel maintenance class from Mack Boring was invaluable, highly recomended!