Good news/bad news... bad news first - The mechanic/technician from W.W. Williams called me this afternoon and said he had researched my symptoms and it sounds like I need a new shifter module. His location did not have one in stock and the closest location that does is in Alabama. He's having the part air freighted in to arrive tomorrow and is having it delivered to his home. When it arrives, he will call me and arrange to come to Woodstock and put it in (he is in Atlanta - about 30 miles from me).
Now the good news - he told me that I could try using the blunt end of a writing pen to push hard on the "D" pad and sometimes that would work as a temporary work-around. I grabbed a pen off my desk, headed to the bus, started and warmed her up, then held my breath and used the pen to push the "D". After poking around (literally "poking it with a stick") a bit, it clicked into gear! Yea! To make sure it wasn't a one time fluke, I shifted to Neutral and then poked "D" with the pen again and it eventually went into gear! Success! Now I was feeling brave to I took her to get fuel and then brought her home to load for the trip to Chattanooga tomorrow. We will decide what to do about the W.W. Williams guy coming out tomorrow depending on what time the part arrives. If it arrives in time to still get us on the road before 4:00PM, we can make our commitment in Chattanooga tomorrow night. If the part arrives too late to get us safely on the road in time, I've decided to take my chances with the "pen poke" work around and have the shifter replaced next week after we return.
Once again, thank you to all our POG buddies who responded with info, advice, and suggestions! You're the best! :D