I'm using Cotonti (Siena 0.9.2) at the moment, but i'm wondering what the best way is to accomplish this.

I'm looking for a way to get everything in 2 languages, including content that is being submitted by admins in articles/pages.
Content in a second language has to be added manually and not be translated by an API.

Are there any possibilities for this?

Update: Pieter posted in the Dutch section that a plugin named i18n by Trustmaster is already in the Siena package and is capable of doing this.

Are there any detailed instructions on how to set this up? I tried following the instructions in this article, but couldn't get it to work and was getting lots of errors. After editing the .htaccess and urltrans.dat files I get a 500 Internal Server Error.