It took a few more hours of poking, prodding, reading and trial & error, but I think I am finally gaining some headway in providing customizations, and even dynamic ones at that. Of course, along the way, I made some wrong turns, and went down some apparently blind alleys, but every error-path turned up something useful – just not necessarily useful to me right now.
One of the alleys I followed included a process of making the OS (in this case, Window 7) think a .docx/docm file was a zip file, in order to add some material to it. That wasn't a direction I needed to be heading but…
Everything old is new again (according to Barenaked Ladies), and apparently everything recent is new, too. Making the OS think a document is a zip was the way in which I was able to crack it open and peer at the XML innards using OpenOffice. It seems that is the way of Microsoft Word 2010, too. In addition to recalling my VB/VBA/MS T-SQL stuff, I guess I get to leverage my more recent knowledge of XML inside a document.
I don't know for sure if I can play directly with the XML at this point, as the direction wasn't where I needed to be heading at this time. But you can be sure I'll be purposefully looking down that alley in the near future.