Some closure to this thread for now: I decided to reinstall NetBSD 4.0 from scratch, this time with a more comprehensive selection of "sets". (My first install was pretty minimalist.) For whatever reason(s), I am not seeing the plethora of issues I had previously when trying to install binary packages.
Anyway, thanks to both of you for providing feedback for me to mull over.
I'm posting this from my NetBSD 4.0 laptop.