Hi Chad, you should be able to do this if you have access to the backend database, through phpmyadmin or similar.
Look for the mdl_resource table, find the resource(s) in question, edit them, and change the type to html (you'll need to type it in).
You say "Many of the resources...", so I'm not sure how useful the next bit will be, but uf you want to convert ALL your text resources to HTML, you can run a sql command to update them - it would look something like...
UPDATE mdl_resource SET type =html WHERE type =text
but use that with extreme caution!!! - as I said, it will convert ALL your text resources to HTML and that may be a step too far! And sorting out the mess will be a nightmare.