my experience is that teachers don't have html files for use in the courses. Mostly they have documents from their office programm.
If they have a single html page, they can add them in the same way like a PDF or Word file.
If they have a set of html files they can zip them, unzip them in a course folder and link to the star page (mostly index.html).
I'm training lots of teachers in using Moodle. Most of them say its very easy to work with Moodle caused of processes that are similar to their normal work in classes.
German teachers are not very familar with ICT, but they can work with Moodle. There are a lot of critics about usability within Moodle from me, but no morethan in the latest MS Office. Did one of your teachers ever try to open a file in new Word or Powerpoint?