Took me a while to figure out what size socket I needed, but finally got the nut off the sprocket. (It's a 30mm, for you other GR riders out there who haven't changed their sprocket yet.)
Had my son stand on the rear brake pedal and used a long breaker bar on the nut. Got it off relatively easily. Now I have to figure out what size spacer I need to retain the 530 chain with a 525 sprocket.