The browser is implemented in a XUL file called browser.xul ($FIREFOX_INSTALL_DIR/chrome/browser.jar contains content/browser/browser.xul).I completely misunderstood this and trying to figure out where I was supposed to create my browser.xul file. They are just saying the the browser itself is an xul file.
Next hiccup was in creating the link in the extensions directory.
One line text file. The content is the path to your addon (including trailing /), and the name is the email-like identifier.
I missunderstood and put the identifier in the content. Let's just say you shouldn't do this. :)
Confused my Mac a great deal.
Finished working through the tutorial and successfully created a barebones Extension!