Check:

http://club.vmag.com/ubb/Forum39/HTML/003154.html

You may as well check the level (drain/fill plug is the allen bolt on the front/left side of the rear of the nose cone). If it drips out, it's full.

I feel pretty confident that you don't need to change it very often, but I wouldn't wait the 100k that Magnuson states. I'm thinking more like every 10k - 15k.