Well, we got a second opinion on the Taurus transmission. Our mechanic took it to a friend and fellow mechanic who specializes in transmissions, and he said it seems fine and what we likely experienced was a computer hiccup where the computer thought the car was in a different gear than it actually was for a second. It happend a couple of times, only while starting out from a stop and right after putting it in gear. And it hasn't happened since a few weeks ago.
So that, my friends, is cool.