I have done some, mostly on early 50's not too many problems now days. Unscrew rotary union fitting, unscrew rotary union, take bolts out from around piston. Get a strap to hold outer sheave in place for when you pull piston off. The piston should now slide off, however there are 2 orings between it and the shaft so it may be a little stuck to them or the shaft. On a 60's it should be antiseezed from the factory early ones were not and needed much talking too with a large hammer to get them to let go lol. Once you knock it off just pull the piston apart and replace the seal inside. Make sure to put it in the right direction is all. Use some kind of assembly lube and knock it back together and thats about it.