I'll answer my own question here after FINALLY getting Moodle installed. The problem (according to the computer systems expert who actually did the installation) is that the instructions were written more for installing on a server rather than within a website. Well, my site has mysql and php and all the requirements for a seamless installation, so it went beautifully in the hands of a skilled expert.
Now, having seen an installation, I think it would even be possible to replicate it!
Watching the installation and then "powering up" the program myself, it is abundantly clear Moodle is an exceptional program. Plus, over the last two days, I've been navigating between my "administrator" account and the account of a fictitious student, and Moodle is very intuitive, both for administrator and student.
I'd say "congratulations" to Martin for having written a wonderful program whose installation actually "falls into place" in the hands of an expert!