Undo the (2 sizes) of allen bolts around the stator cover.
Use a big Allen key, remove the centre cap.
Before doing anything else, put something on the centre of the rotor you can see through the cap. When you pull the cover off, the magnet will want to drag everything else out with it, meaning stuff may fall straight into the case.
Keep pushing hard on the shaft, (or better still, get an assistant) while pulling the casing off. A screwdriver, or socket extension bar or anything that will fit through the hole will keep the rotor in place when the stator comes off with the cover.
At this point, I'd put a piece of plastic or cardboard over the hole to the crank. There's 2 spacers and a washer at the back of the rotor that your going to pull out to replace it. As well as some rubber cush drives. On the off chance it separates, it won't fall past the cardboard.
Once it's all out, pull it apart, swap rotor out and put it all back.
I had to put it in gear and wiggle the rear wheel to get the cogs aligned and it all to slot home.
Remove cardboard, button it up.
You don't have to drain the oil, but some will escape so put a rag down. You might want to dab some oil on the parts as you reassemble into the bearing.
Good luck!