I've managed a grasp on most of the Warhammer stuff, but I have a hard time figuring out what tech-priests are like.

Are there any novels that feature them in primary roles?

As novels there are Titanicus by Dan Abnett and Mechanicus, but the latter is a Heresy book.

Here is something on the Tech-Priest.

Some on the Adeptus Mechanicus.

Hope it helps.