If you find that you do need to remove the bobbin assembly ring, I was able to do this successfully just this week by following Rain's tutorials where he clearly shows the tools to use and how to disassemble and then reassemble this area. His blog is at
http://vssmb.blogspot.com. VintageMotif wrote about his blog back in August 2012 and I'm so glad she did since I've found his site to be very helpful. Just look on the right hand side under "labels" and you'll find the link to the 201-2 tutorials.