I've had them completely serviced for $100 - they are no big deal to fix - a routine camera to repair.
Yes and no. (Camera tech here).
The camera isn't difficult at all to diassemble for service. Rather easy.
Something like cleaning the rangefinder glasses or cleaning the escapement (so the slow speed work again) is also very easy to do and I'd say even you could DIY.
However, getting the top speed (1/1250) to work OK without resorting to the unethical, dangerous, toxic measure of "increase the curtain tension until the top speed works" is not easy at all. Thus, many, MANY so called "camera techs" will just increase curtain tension. Which is an extremely easy thing to do.
Sadly, this can risk your camera become inoperative in short time or damage the main (tension) springs forever, not to mention to increase wear on the mechanism. You can easily detect such a camera: the advance knob is stiffer, the sound isn't gentle and quiet but becomes a loud "quack". All the fineness of the Zeiss machine is gone.
Besides from that, this camera can be calibrated for very accurate shutter speeds from 1 to 500, however, it seems that very few technicians understand how to, because there is no official documentation out there to tell you (the so called "service manual" doesn't say any word about adjustments). I'm collecting information on how to calibrate this camera on another forum.