I thought I was the only one to have a final drive failure, until I read
@bikecrazy 's post here. The seal leaked on mine also. It's rare on these bikes, so I wouldn't worry about it. I'm just unlucky. I also replaced the drive shaft later.
Head all the good advice here and change the final drive fluid regularly (cheap and easy) and grease the splines of the drive shaft with every rear tire change. The first time you check it'll probably be just dust, which is no bueno. You'll want to use a high moly content grease. The procedure is pretty straight forward. It's in the manual and there are lots of posts on the topic on this site. Look for opinions on grease and tricks for lining up the drive shaft with the final drive.