One of the nice things about vB 5 is that admins have the ability to control the way their site looks through the use of the modules (widgets). They can place things where THEY want them, not where a coder/developer thinks they should go. So, you're better off creating a widget to hold your content and let admins place it where they want it. Even if they must create a page to hold the widget.
If you go that route, you simply need to create the module (widget) and a widget template. Then code your API to handle the info displayed in the widget.
In cases where a page must be pre-defined and nothing can be moved around on that page you need to create a page, a page template, a page route, a system widget, a widget template and a widget instance ID. In your case you would also need to add to the headernavbar column of the site table. All of that needs to be done in the install code for the product. At this time, there is no way to add a navigation link or page via the XML itself. And at this time, the widget instance ID must be created in your API. I think I got eveything there.