Glad to help out, and good to hear that the issues appear to be minor
If you're going to replace the o-rings of the shocks, I can recommend going for the X-rings: way smoother and they seem to keep the oil in better, too.
As for the ball diff: There are plenty of guides on Youtube that could help you. The short story is:
- It's worthwhile to sand the main diff plates with fine, wet sandpaper (600 or higher)
- A layer of grease on both diff plates is enough - the thrust bearing can use a good dab of grease so the balls stick around the diff screw.
- Compress the diff spring a few times before the diff assembly.
- Make sure the slipper slips (a whizzing noise) and not the diff (a screeching noise). When holding both wheels, the slipper should be tight enough to just lift the front end off the ground (do keep your face wel away from the car: it can very suddenly lift up if the slipper grips or is too tight).
- Run the diff in outside the car with a cordless drill (and a driveshaft) or re-check the diff setting/tightness after a few minutes of running.