Thread:Project:Support desk/How to localize things like "Contents" and menu labels?

Hi, guys! I was wondering how I can localize all of the Mediawiki-generated content on local language wikis. This is the url to the wiki: http://translations.ted.org/wiki/Main_Page

As you can see, there are multiple language versions, with English being the main one. There is content in other languages, but for example, in this Spanish article, the heading of the auto-generated contents list is "Contents" rather than "Índice." Also, the interface is not localized (so things like "Edit," "Discussion" etc. are all in English). How to fully localize the local language sections?

I've read the wiki family guide, but I am not sure I understand the process completely. If I install the separate wikis for each language, do the users have to translate things like the word "Contents" and the menu labels on their own, or are there already localized versions that I could use? Also, if I were to do this with the existing wiki (the one linked to), how do I preserve the existing content? So that if I end up installing separate wikis for each language, I will still have the same content in the Spanish wiki. Since it seems that this would create new domain names for each language, is there a way to globally rewrite URLs to point to the right articles in the language? I am a beginner at Mediawiki, so I may be missing something obvious.