I bought an ETR in ebay and among other problems that I would like to take care of are the following: 1) The 75mm MC lens has some dust inside the elements I'd like to clean. 2) Aperture ring is very hard to turn and I'd like to lubricate it or get it to operate in a smoother fashion. Does any of you have some experience performing any of these tasks on the Zenzanon lens and would care to share it with me? _ Is anybody out there that could help me getting a shop manual for these lenses?