420C Rock shaft

[420C-Mike]

I am finally starting to reassemble my 420C focusing initially on the undercarriage and getting the Deluxe Seat installed. The first step is to get the rock shaft assembly installed before mounting the seat. I have a number of questions regarding the rock shaft and would appreciate the members insight and suggestions. For those with a copy of PC505 parts manual I am referring to page 55-42 (Note: the Service manual has little info related to the Crawler version of rock shaft.)
1) Is there a trick/method for removing the retainer ring (key 6) without damaging it? The unit leaks and I need to replace the seal.
2) Does the dowel (Key 20) serve any purpose other than alignment for installation? Mine is ground flat in the housing and not readily removable. I assume the mounting bolts provide most of the structural mounting shear strength.
3) Is the "pilot" (key 31) needed. I do not have one and when I removed the upper cover to install the support (key 30) it is open to the inside of the case.

Appreciate any insight and suggestions- Mike