I am new to GitLab and Markdown. Is there a way to automatically insert text into pages in the wiki? Can I make a .md file and put some text in there and add in some markdown to pull the text from that file and put it in the page I'm working on similar to how the images work?
For example, if I want to have my contact info/email address at the bottom of every wiki page, can I do that?
Unfortunately not directly through the web editor. You can try Gollum which supports shared headers and footers. With Gollum you can build your wikis locally and push the built version to the remote.
More about subpages.