[wiswind]

The tranny is very sensitive to low fluid, so that could have been a factor.
Another thing that has not been mentioned is the Transmission Range Sensor (aka Neutral Safety switch).
The vehicle speed sensor is the one that is located above one of the catalytic converters......on the back side of the transmission case.
It is not an expensive part, but is very hard to get to, it would be super easy to change, except that it has a very bad location.