how to changeout water pump shaft seal??

[Sweepea]

2016 350 RR. I'm getting oil in my radiator fluid and am guessing it's the water pump shaft seal. Can you change out the seal without removing the side case? Can you just remove the water pump cover and impeller, and pull the seal out from the outside? Or, do you have to remove the side case and replace that little o-ring on the back side of the water pump case too?