You can do this, but it will be helpful if you have a little experience with PHP code - not that you will modify much code, it will just be a little less scary!!
You need to create a language file, perhaps called language.php - I would put it in the include directory.
Open main.inc.php, and find #include required files
Add require(INCLUDE_DIR.'language.php');
Now what you need to do is find where you want to translate words / phrases. Each time you find a new word or phrase, you can add the translation to language.php in this format:
define('ADD_NEW_TOPIC', 'Add New Topic');
Then replace the original word or phrase with ADD_NEW_TOPIC and the translation should appear.
Really, the trickiest part of this will probably be chasing down all the different files which contain the words you want to translate. There are text editors out there which will make it much easier - I use 'Crimson Editor' (because I like it, and it is free). It allows you to search a folder and find all occurances of a particular phrase. So I could search for 'Add New Topic' and it would show me all the files it occurs in.
Let me know ifyou need more help with this!
