I don't know if they have already told you to clean all the grounds or not; if not, then that should be done.
On the crank sensor, they can do funny things. On my sister'* 98 LeSabre, I drove the car, started cold no problem. Drove it 8 miles, parked, went into a shop, came out, it started, drove a mile and it stalled. Started back up no problem. Eventually the car died completely and it was the crank sensor.