On left hand side (when seated on tractor) about 4-5 inches up there should be a square headed, 1/4" pipe-thread, plug for checking oil level.
On the same side and at the bottom of the housing and slightly forward of the level plug will be the drain plug.
Not a bad idea to tap a little oil off the drain plug to check it's colour. Sometimes a bit of water will come out (from condensation?)
On the right hand side (brake side) near the top of the housing is a 2-position ~3" lever. It can be horizontal or vertical. Should be in the horizontal postion for "position control" of the 3-point linkage. Vertical is for attached implements like a plow. Dexta's have a suction screen and an internal screen type "exhaust" (oil is filtered as it is returned to the differential housing.)filter for the hydraulic pump. (I believe you have to pull the top of the housing off to get at them.