Thank you, Ward Baxter, for listing those font filenames!!!With that information (where is it in the documentation?), I realized that several fonts were never installed in my setup of Finale. So I did a reinstall.
And that helped me to solve my problem. I am positive that there is no place in the documentation (up through 2000a, which is what I'm now using) where all the steps are listed on how to change one notehead among many, so I'll list the steps here.
1. After entering the basic notes you want, go to the OPTIONS Menu item
2. Select "SELECT DEFAULT FONTS..."
3. The third item is for "Notation" - Maestro or whatever the default font is should be selected; click on the SET FONT button off to the right
4. Find EngraverFontSet -- select it and click the OK button
5. Back in the SELECT DEFAULT FONTS window, click OK
Now, back to the music:
6. Click on the Special Tools Tool
7. The Special Tools toolbar will appear; click on the Note Shape tool; then click in the measure where you want to alter a note; Each note in the measure will receive handles.
8. Double click on the handle of the note you want to change -- the Symbol Selction window will appear, showing you the Engraver (or whatever font set you've selected).
9. Double click on the note you want-- AND THAT'S IT!
Now what I still want to know is this: The documentation (chapter 28) indicates that if using the alternate font set as Articulations, that these can be entered with keystrokes, e.g. on page 28-5, it shows you that the "let ring" slurs can be entered with either the letter I or shift-I combination. But those keystrokes (or any other) don't work in Articulations. Do they mean you have to enter them as text?
*Sigh* what a good technical editor could do with that documentation.