Happily, I was able to eventually get the tumbler to turn to the second detent (the “ignition on” position) and ultimately remove it without going through the “can’t get the tumbler to turn” (horrifying) procedure discussed at dieselgiant.com.

Briefly:
1. I removed the key itself from the black plastic “fob”. This way, I would more easily and effectively deal with it during the procedure.
2. I acquired a hand orbital sander (item #40070) from Harbor Freight (around US $10.00).
3. I turned on the sander while touching the vibrating part to the key. I just worked it back and forth on the key for several 30-second periods. BE CAREFUL TO HOLD THE SANDER SO AS TO PREVENT IT FROM TOUCHING THE INSTRUMENT CLUSTER FACING AND/OR DASHBOARD AND DAMAGING IT/THEM.
4. Carefully, I used a pair of pliers to grip the key head and turn it left and right repeatedly in an effort to ultimately get it to turn to the second detent. This didn’t work the first few tries.
5. I repeated steps 3. and 4. multiple times.
6. I sprayed some Wurth HHS 2000 lubricant into the key hole. Several days earlier, I had done the same thing with WD-40 and let it sit overnight.
7. Eventually, using the pliers and carefully gripping the key head, I was able to get the tumbler to successfully (without forcing it) turn to the second detent.
8. The next step was to insert a straightened small paperclip into the slot on the side of the tumbler so as to force the pawl located on the side of the tumbler to retract. This is required so that the black metal ring on the outside of the tumbler can be unscrewed. Remember that you must keep pushing in the paperclip (that is, retracting the pawl) until the black metal ring is completely unscrewed. NOTE: The instructions stated to line-up the slot on the tumbler to the second detent and then insert the paperclip to force the pawl to retract. This was not helpful and didn’t work. I used a very bright light while carefully turning the tumbler until I could see down the side of the tumbler and discover the hole where the paperclip would go. It turned out that the tumbler had to be turned back a bit toward the first detent in order to find the pawl hole.
9. Next, the tumbler and black metal ring lift out of the car completely.

Miscellaneous:
A. I’ve yet to find ignition tumbler replacement instructions in the factory manuals. Instead, I used the Haynes manual (moderately helpful) and the dieselgiant.com instructions (most helpful).
B. With the steering wheel locked, I had the vehicle towed on a flatbed to my garage. There was no way I could do this work without ready access to my tools, chemicals (lubricants), lighting, and 110v power. The tumbler locked-up while the vehicle was in a parking lot about eight miles from home.
C. Once I had the tumbler and black metal ring removed, I did a thorough cleaning of the insides of the ring and what it threads onto since both were well coated in lubricant from earlier work.
D. I had one heck of a time getting the large electrical connector located on the back of the ignition assembly to release. First, the clearance is awful there with the black plastic hose that connects to the left dash vent. I disconnected the hose at the console end and pulled it toward the driver’s door enough to provide clearance behind the electrical connector. Next, you may have to gently and carefully wiggle the key/tumbler a bit in order to get the connector to release. Whatever you do, don’t force it out the connector.
Once I have the replacement tumbler/key from Phil, I’ll be re-installing. From the looks of things, that work should be substantially easier.