The oil is checked through a drain plug in the bottom of the drive. You can't tell the oil level without putting more oil in and opening the top oil screw. When you change the oil you just keep putting more until it comes out the top screw.. It is a good idea to check the oil and see how it looks. The oil condition can tell you the health of your drive.
Check over the bellows for rot and rips.
Grease all the zirc fittings with marine grease.
Where did you see water coming out when you ran it? Did the temp get too high?