TT
The timing change is done by loosening the timing ring, which is just next to the crankcase but in back of the prop hub, which contains the magnet which triggers the sensor. I can see it in your picture. There is s set screw that can be loosened and then the ring can be rotated. If you haven't moved it yet, don't. Wait till you scribe a mark on the hub and case so you can put it back where it was originally. Also, I bought a hall sensor from Keith at BME this last summer, mounted, with a deans connector, for $13. He said he had lots of them, so I am assuming that whoever buys BME will get that large stock of sensors.
Hope this helps.
Sam