That will require you to unscrew the barrel from the focus mount; remove retaining ring that the shims sit on- 1 screw. Be sure to Mark the orientation of the ring, I use an arrow. Unscrew the retaining ring, then take out the screw that links the aperture ring to the underlying mechanism. Remove the ring- see two set screws holding the name ring in place. Mark the positions, I scribe a mark in the barrel. Remove the two set screws- the namering unscrews. The front element comes out, as does a spacer and the middle triplet. "Done"
Many thanks, Brian - super helpful!