Not too long ago my stator went bad as well as the rectifier/regulator. I replaced both from Cycle Electric. I had a great experience talking to them and they sent me to a distributor near me. One of the things I like about their kit is that it relocates the rectifier/regulator away from some of the heat.
As for the engine oil, I'm pretty sure that the only place that could leak into the primary is at the main seal. I just had to replace that too. If I am not mistaken, there are two seals between the transmission and the inner primary. One keeps fluid in the transmission and the other keeps fluid in the primary. (I think that is how it is set up. I haven't had to screw with that yet.)
By the way, the main seal replacement was not a bad job at all. I got the Jims USA seal removal/seating tool and that made it quite easy.
Ride safe.