Servicing a Carl Zeiss Jena M42 preset Biotar 58/2

[Seele]

It was some time ago that fellow member chris_zeel posted a thread on servicing a pre-set Zeiss Biotar 58/2:

http://forum.mflenses.com/preset-biotar-m42-disassembly-t70261.html

I am facing the same scenario now. Just to be specific mine is the M42 screw mount, "fat" version with scalloped focussing ring, serial number 3948256; I have had it for years but now I think I should pull my socks up to attend to it.

The focussing ring is getting to be sticky to turn, if I can have it apart then I should be able to get the old grease removed and replaced with Helimax XP. More of a worry is that the aperture ring is stuck solid at full aperture: the preset ring works and can get the limiter dropped into the aperture values but that's about it.

Unlike the semi-auto version it does not have the screw on the side of the barrel, as seen in tomasg's example, and I am sure the innards are very different for not having any mechanism to drive the iris from the camera:

http://forum.mflenses.com/stiff-focusing-ring-on-a-biotar-58-2-no-problem-t24157.html

I do not seem to be able to find any tutorial regarding how to take the lens apart, and I sure would not want to be foolhardy enough to paint myself into a corner. Any help would be greatly appreciated; thank you!