Hugh,
What stopped working, exactly? It's not that unusual for these very old cameras to develop problems. Some problems are less serious than others, however.
If the problem is a stuck shutter (or slow to open and close), then sometimes they can be revived yourself, if you feel inclined to open it up and perform a little surgery.
If you send it off to be repaired, it depends on where you send it, etc, but apparently the going rate here in the USA is about $80~$90 for a complete CLA that includes most non-parts required repairs. Your milage may vary.
Of course, if you pop for that much for a CLA, you'll be getting back a camera that is essentially just like new.
Best Regards,
Bill Mattocks