I have the bike stripped down now and the clutch is out (except for the clutch housing as I still need to make a tool for that). It only took me 3 days but with a lot of re-reading, picture taking and otherwise not turning wrenches time in the garage.
The clutch doesn't look contaminated, nothing leaked into the clutch.
The only 2 seals that were leaking were the one that goes into the slave cylinder pushroad (there was some transmission oil under the slave cylinder)
and output transmission seal (there was some oil in the swingarm).
And, the friction plate is still above the service limit -- 5.4mm (service limit is 4.5mm).
So the question are -- why
did it slip and what should I replace? The surfaces on the cover plate and pressure plate look worn but smooth. Looks like there is some heat discoloring, but I don't know if that is abnormal and indicates need for replacement by itself. The plates(cover/pressure) surfaces are very smooth to the touch, but have some "polished" spots.
The friction plate is worn differently on different sides:
What does it tell you?
Anyway, the clymer said that another reason the clutch can slip is weakness of the spring plate. I don't know how to test it, but I guess I need to replace it just in case.
The most important question for me now is -- should I replace the pressure plate and the cover plate? Opinions? Experiences?
more pics are here -> http://nedod.fomac.net/other/k12gt/clutch/