My M6 is out slightly at infinity as well, although it's not too far out andf I haven't had the nerve to try to correct it myself yet (and yet I CLA my own lenses...). It's not supposed to be too difficult, but without the tools is a trial and error thing. The eccentric on the roller adjusts infinity, and the screw at the base of the arm for the rest. From my understanding, adjust the eccentric till infinity matches, then check something close at say 1 or 1.5 meters. If that's off, adjust the arm and then the eccentric again for infinity, repeat 'till correct. Sounds too simple really, but it should be all that there is. I was also told than in most cases it's just the eccentric that goes off, and so in most cases you don't have to touch the arm.
I think I may try adjusting mine after this block of summer classes end and I don't have to use it every day, just in case...
Gerald