Hoi!
None of these steps are required before changing the language code in MediaWiki, as I have done. Localisations in MediaWiki are identified by RFC 4646 tags, and no significant difference between variants is required.
Yes, as said before :) Language files are quite automatic :)
Berto 'd Sera Personagi dl'ann 2006 per l'arvista american-a Time (tanme tuti vojaotri) http://www.time.com/time/magazine/article/0,9171,1569514,00.html