q.1 Yes I used to change the seals all the time, the seal is a ceramic disc, Dont recall if there is a special puller for the York, I think there is a plate behind the clutch that comes off by taking out a couple of screws. Changing the seals never seemed to make much difference, York compressors are by design a leaky contraption.
q.2 Auto parts stores or Auto a/c specialty shop. The shaft seal is available alone or in a complete gasket set.
q.3 The oil in the York compressor sump is the same as the refrigerant oil that circulates through the system. The oil is under pressure from the refrigerant, so if a little oil is leaking out the seal, a lot of refrigerant is leaking out there too.
q.4 A York besides being,leaky,noisy,obsolete 1950's technology, also only displaces 4cubic inches per revoloution. The Sanden is somewhere around 6 cubic inches. more volume = more cooling.
Al Lieffring
66 230Sl
Jones'n for a new gas tank