As Paul suggests, this is not at all straightforward. It also works better if you start with the first document and not a new document based on the normal template (or at least create your new document using the first document as a template and replace the document range with the content of your first document).
Inserting a section break is easy enough, you just add it to rng before you insert the file, then reset rng to the end of the document again.
Or you could use
http://www.gmayor.com/Boiler.htm