I was able to get the back covering off at least. The first step is to fold the seat down, then there is a long press fit closure at the base of the seat back that you can just work apart. At that point, you can dig around with your fingers for the zipper pulls on either side of the seat and unzip them, which will let you access the internals of the seat from behind.
I couldn't figure out how to disassemble the seat any further than that, but in my case it was at least enough to positively identify the exact part that was rattling so the service center could take care of it without guesswork.
I know this reply is a bit late but I hope it's helpful.