Headlamp update
I finally got a few minutes to look at the headlamp problem again and this is what I found. First, replacing the headlamp involves disassembly and removal of the front bumper and grille, which is a lot of work for a simple job. Something to be done only as a last resort, so I removed the protective cover just behind the driver side headlamp and was able to see the back of the headlamp assembly. I could see that the up/down adjustment gear was turning ok, and it was not slipping on the shaft. I then checked the lo beam lamp and discovered that the whole lamp assembly would move up and down about a half inch, against spring pressure. You can see this also by looking down into the lens from the top, and you can see the entire reflector moving. I had learned in my research that the adjustment mechanism can be broken if someone turns the adjustment too far. This apparently is what happened before I got the car. I then started turning the adjustment while continuously moving the reflector up and down manually, with the hopes of reengaging whatever was broken. I was able to find a tight spot where the reflector jammed , and the reflector is in a good enough position to be satisfactory for headlight aiming. Almost never happens!

So far, a weeks driving vibrations have not shook it loose.
I am going to look for a cheap headlight that I can disassemble to see if this problem is repairable permanently. If this results in any success, I will post how to do it. The price for new headlamp assembly is high, and you must get a factory part to be assured of quality. If it is a chinese knockoff, it is not called " chinese junque " for nothing! BTW, I also polished and cleaned my lenses to clear them of age dinginess. Use wet sandpaper, 1500 grit, first, keep it wet and lightly remove a thin layer, only takes 2-3 minutes to do. Scary the first time. Wash it off. It will look frosted, but dont panic. Next, do the same thing again, wet, with 2000 grit. Wash it off. Next, do it again, with 2500 grit wet/dry sandpaper. Wash it off. It will still look frosty, but not as much. Now, get some Meguiars PlastX clear plastic cleaner and polish and a Powerball mini polishing sponge ball for your cordless drill. I got both these items at my local Autozone ( Powerball, about $25, PlastX about $8 ) With a cloth apply the Plastx to the lens and polish by hand for 1-3 minutes, and then buff with the powerball on high speed while slightly damp. Before buffing, get some blue painters masking tape and cover up the paint around your headlights to keep the buffer from removing any of the body finish. Finally, use some good carnauba paste wax on your headlights to keep the brown film from coming back.
If I find out how to fix these headlamp assemblies, I will post the information.