Even though you have been scammed by a crook, it might be just as well to get the camera fixed (by a genuine tech). It will put your overall cost above what you should have paid, but after a true service from someone like Don (DAG Camera Repair) you will have a camera that will last the rest of your lifetime. It is a nice thing to do for the camera as well...the last guy was not worthy 🙂 It sounds like you might be the kind of person who will keep the camera and actually use it on a regular (daily?) basis. If that's true, the higher cost of your camera after service will dissipate over time.
I'm really sorry about your experience. Personally, I would be quite bitter and vengeful. However, don't take it out on the camera. If you can warn others to be wary of this dishonest seller, that could be useful, but be careful not to go as far as slander. Again, I would be very bitter, so that's hard advice to follow. Even if its my own.