There are already tools to convert docbook to markdown (e.g. pandoc), so they have to be applied. The results have to be checked whether they are useful, and then every chapter should be a single wiki article, with one overview, such that the user optimally doesn't see the difference between the website and the wiki guide.

The guide: http://www.netbsd.org/docs/guide/en/index.html

The sources: http://cvsweb.netbsd.org/bsdweb.cgi/htdocs/docs/guide/