Essex camera in New Jersey will also service them. The shutters tend to require less service than the Leica's. The viewfinders get some haze under the front glass, but I have cleaned those out myself. NEVER lube the focussing helical. The proper way to clean it is to drop it into gasoline. After removing it from the camera, of course. If you need one that has to be serviced, send it to a place that has worked on them like cameraquest or Essex.
The S2 finder is terrific, brighter than the SP. The SP has parallax corrected lines for the 5cm, 8.5cm, 10.5cm, and 13.5cm and a built in finder for the 28 and 35. If you are shooting with a 50, go for an S2. If you use a lot of lenses, look for a user SP. One in a 7/10 or 8/10 "user condition" will run about double the price of a 9/10 S2. But the finder is easier to use with additional lenses.
But using an S2 with external finder does work, even at a playground:
Nikon S2 w 13.5cm F3.5 Nikkor, wide open: