I've just stuck a copy of my on the fly translation script which I adapted from the simple thoughts wordpress plugin into a zip file which you can get here:
I'm afraid to get it working on your site you need to edit all the index.php files individually to change:
$MySiteURL = "http://www.articlecodex.com";
to your own URL.
Also you'll need to create an "en" folder and set it up with a page that simply redirects to your homepage.
Then all you should need to do is upload the entire translate folder to the root of your site and point your browser at http://www.yourdomain.com/translate/fr/?/ to see a french translation of your site.
It does this via the google translate site on the fly and you can see it working here: http://www.articlecodex.com/
Let me know if you have any problems..
Edit - I don't know how it will handle URL's with large query strings to be honest. I have played around with this a bit but as my site is designed to not use more than a few basic querystrings I haven't played with this much.. There is also a line in the code of every page to convert my charset which you may or may not need to adjust.