92 Ciera 3.3L V6 160k

Starts fine, start driving down the highway the speedometer suddenly drops off and it feels like 20 horses up and died. few seconds later the service engine light will flash and the speedometer come back up and the horses are resurrected. When I slow down or stop the car dies and won't start again until it cools off. Had a diagnostic scan done on it and it says the "Vehicle Speed Sensor" is bad. Would this cause the car to die, or do you think I have more than 1 issue?

Thanks for any help.

I replaced the speed sensor and I think that fixed the speedometer issue, but my car still dies. The trouble code being displayed now is "Electronic Spark Control (ESC) Circuit". Any ideas?