To check the oil level, put a finger inside the fill plug and feel if the level is near the bottom of the filler hole—0.5 in (13 mm), according to the owner’s manual.
If you must change the oil, remove the drain plug, let the oil drain completely, reinsert the bottom plug, and refill from the fill plug until oil starts to come out from the fill hole. Before reinstalling the plugs, clean them thoroughly to avoid contamination inside the final drive.
Since the plugs are under a lot of vibration during operation, ensure they are snugly tightened so they can’t come off.