A project I peeked into but never started.
This is a simple guide, made for my reference but carefully documented for others to also use.
Regarding MediaWiki version 1.15.1 or a little earlier.
How to rescue content from a MediaWiki wiki.
This was a failed project; it was impossible to automate so I ended up pursuing this by hand.
[ + ]
This was an aborted project to look into leveraging ways to use MediaWiki by outside influences.
How the admin can change someone's password.
The built-in "forgot password" feature will work for most people to change their own password. But this is useful for locking out users.
My rough notes are found in MediaWiki reinstallation notes. This page is a straight line to success for me. If things don't work out for you, it's possible that I explored some other paths which might work for you.