@MontereyJack,
Here in the post-holiday solitude, I thought I would revisit this posting, starting off with the good news that Santa left me a
Audiovox Corporation CRF907 RCA Compact RF Modulator in my stocking this year - which was strongly suggested as being the "intermediary" device that would allow me to finally complete the installation of my DVD player, and get it to work with my older TV, which only has a 75 ohm, coaxial input connection.
The modulator goes together pretty quickly (the benefit of no moving parts), and after running the 75 ohm connection from the converter box to the TV In connection and the 75 ohm connection from the TV Out (to the TV), along with the RCA cable connections from the DVD player to the modulator (and plugging in the power adapter), a test of the installation initially suggested we were still
not quite there - since the DVD was successfully transmitting audio, but not video.
A quick re-review (combined with a little intuitive deduction, based on the fact that audio
only was now working), revealed that although the rear connectors of the DVD player were "color-coded" for standard RCA-type connectors (white, red, orange), as was the modulator unit, it was necessary to plug the orange cable on the DVD into the Video Out plug, which was grouped with the Component Video connectors (Who knew?).
So, the good news is that this brings this issue successfully to closure (hopefully for the benefit of others), and when faced with this problem the purchase of the RCA modulator (<$10), proved to be the winning solution.
Hopefully, now my wife will stop calling me colorful names for having invested in such a low-end Sony DVD player . . . although that may be too much to wish for (too bad RCA doesn't make a modulator to fix
that problem too). Thanks for everyone's help on this!