I don't know what happened to the other replies that had been here before, but I want to thank all who responded.
I finally got it repaired, and I was right. It was a sensor that dealt with the car's speed. I took my time and found a reputable trans repair place and they did the job. I was sure I didn't need a new transmission. They replaced the sensor as well as a filter and put in new ATF. The car now runs just as good as it ever has. The cost was nearly five bills, but that is about what I expected it would cost, so I don't feel like I paid too much.
Thanks again to all who responded to my plea for help.
