Permanently change 'MediaType' for iTunes

How do I permanently change 'MediaType' for iTunes?
e.g. I want change some MP3 files (not MP4) mediatype to 'audiobook' instead of 'music' in iTuens, but I want these property to stay with the files, and I don't need to reDo them next time on other itunes from a different computer. Note: MP3 files are stored on a network drive and are shared.

Use the field
and enter one of the following strings:
Movie, Normal, Audiobook, Music Video, Short Film, TV Show, Ringtone

(it's probably Audiobook then)

Please note that this will not make it a real audiobook with all the features of remembering the last chapter and stuff.

This tag only works on mp4 files.

Think this is primarily stored in the 'iTunes Library.xml' file so if your moving your music library around with iTunes then all you have to do is make sure all the drive letters and paths are the same as before and import the 'iTunes Library.xml' to it. Big advantage along with having the exact same library is that all playlists including smart playlists are restored.

I imagine simple stuff like changing the TOPDIR of a selfcontained dirstruc tree can be done simply enough via search-and-replace with a decent plaintext programmers editor.

However for more complex stuff (yes going OT here, sorry) short of learning bare-metal XSLT transforms programming, are there tools out there to facilitate importing/exporting/editing the iTunes XML data store?

I understand going from multi-table CSV to XML, for example, requires pretty decent XML-coding chops. . .

Perhaps the best approach would be to identify which of the catalog/library management tools does pretty complete import/export to iTunes and work through that - any candidates come to mind, e.g. MediaMonkey?