Distributor - Lack of Advance

[lschif]

'78 SC was having "stuttering" at 4K plus RPM. I checked the timing and it appears that I am not getting any centrifugal advance. The advance is around 5 deg. at idle and then "vibrates" around 5 deg. as I adjust engine speed.

I've read a couple of posts about rusty / gunked up advance mechanisms. Now for the question - how do I get to the advance mechanism on an SCs distributor so that I can clean / inspect it? Do I need to drive out the gear pin, remove the gear and pull the distributor shaft / mechanism out from the top? Or, is there another way to remove the steel "contactor" piece? Seems like I am missing something - help.