[mr tickle]

I replaced mine On Saturday and had exactly the same question.
The answer is yes the ABS ring and the plastic cover do come off quite easily and are not part of the CVJ, but you will break the plastic cover in the process.
Just stick a flat screwdriver behind the lip and twist, the plastic will snap and then it comes off.
What was left of my rings was rusted and partially bonded to the CVJ. I had to chip off the rust and then clean up with a Wire brush.
Tap on the new rings and you should be fine.

I think the plastic covers are there to stop ingress of dirt, however I would say that appears to be counter-productive, in my opinion the plastic rings actually allow water and dirt to be held inside and make rusting more likely not less.
I'm willing to be corrected, however even if I had the plastic ring things i would prefer to leave them off, it all works just fine without.