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The way the multilanguage hack works, basically means you don't need 2 seperate sites. Effectively it displays text relevent to the language selected - and ignores the un-requested language.
I would suggest to perhaps do a test install of it first, to make sure you've got it all working fine - before installing it on any release site.
There was a recent news posting on installing the ML patch on modules that don't already support it. If I wasn't very tired, i'd search for it for you (but I am - so I wont!
) - but check recent news postings.