Steve, there is a plug on the side of case to check the level. I run it so it is full to about 1/4 inch from the top of the hole. I use tape or my finger to cover the hole and fill to that level.
I inspect the gears each race weekend and filter the gear lube and reuse it a few times. I use a 70-90 gear lube.
Not that I am the expert on these boxes but thats what I do.
I always drain the case fully (using the drain plug under the diff) and then re-fill with 2.25 quarts. That's the recommended fill level for road courses.
I use Redline Shockproof Heavy. Change it basically once per season.
As Joe has said, there really is no standard. My routine is to drain and check the gears after every 2 race weekends. I use Mobil 1 70/90 and use new fluid each time. Fill until you get gear oil just coming out of the drain on the side, seal it and add 6 more ounces.
Each time you do it you'll become more proficient and it will take less time.