Find and Replace Placeholders in a Word Template

We have a template file that we use as a baseline in our report generation (see here for help creating a new Word document from a template). The template file has some placeholders for title, subtitle, author, etc. I wanted to be able to dynamically replace those with content when the rest of the document was generated. This took me way longer than I expected to figure out so here is hopefully some info to help the next person. First I found the relevant section in the XML (the Open XML Productivity Tools are a great help for this). Then with a bunch of trial and error I figured out how to find and replace the '[Document title]' placeholder.