Well, were you able to fix the opener?
According to what I learned by doing some online research, I think I've narrowed the problem down to a bad RPM sensor.
Tomorrow I'm going to call the Genie help line. They will go through a complete, live, trouble-shooting session with you on the phone, in real time... all you have to do is be standing at the opener and follow their instructions. If their diagnosis is also a bad RPM sensor, problem solved. I'll post the results tomorrow.
I think you are out of luck on this one. I have been told that the door opener parts are difficult to purchase. For safety reasons.
I found a ton of online sources for replacement parts.