I don't believe you have to split the case for that one. Kawasaki's usually do. If you are losing oil and fouling plugs, the right side might be shot. If you are showing signs of running lean then the left one might be gone. You should be able to do a leakdown test to see.
I had one and it would hold 5 psi for quite a while without any loss. If you pull the clutch cover off, you may be able to see of the seal is accessable from the outside. You should have a manual, it can save you from fouling up your bike. I am in the midst of a right crank seal on my 80 rm250 and to get to it you need to remove the crank gear. Without a service manual I would never have known that the threads on the nut there are left handed.