Denny,
Thanks for your comments. In the first place, Lexus has let me down once so I will not be giving them another chance to do the same. Get me once, shame on you - get me twice, shame on me. No thanks!
I must admit that, other than the transmission fluid being darkish, the fluid level had always been fine and I had no problems with the trans until after the Lexus dealer said the trans had a small fluid leak. I had the seals replaced and that is when things started going downhill. After I started having serious issues with the transmission, I did some research on general transmission failure symptoms and causes. I discovered I had experienced almost everything several sources reported, so when the Lexus dealer told me the trans had failed I believed them.
Now, it has crossed my mind that they may have sabotaged my Lexus. Maybe they didn't want to have to work on it anymore. Maybe they didn't want to have to keep telling me they could not get parts I might need in future. Maybe they thought I would purchase a new Lexus from them. Maybe there was no sabotage. Maybe it is time for me to get a new car. In the end, done is done. Time to move on. I wish that next time I purchase a new car I could afford to buy 2, and run the second one only occasionally to keep it viable. That way, I would always have parts available.