When I chose a way to make my site multilingual, I chose Marcan's great hack XOOPS Multilanguage. I'm a satisfied user of this module, but after reading this article and this answer, I'm thinking about changing to XLanguage as it seems that this is the best option for future compatibility.

Would I run into troubles if I change from XOOPS Multilanguage to Xlanguage?

What would be the best way to proceed? Can I use both simultaneous in order to change the "custom smarty tag definitions" slowly?

I've recently passed from XOOPS Multi-languages (Smart Language ?) from the SmartFactory (Marcan) to XLanguage, and had no real big problem.
I still have a Charset encoding problem, but it existed before.
I've got some blank page, and have fixed some of them, and the module MyLinks doesn't work anymore (blank page), but it's recent and i think i'll be able to fix most of those problems.
Then, it's easy...
Replace the files which was hacked by the Official XOOPS ones, add the line into common.php, and it works ! (after installing the module and config it)
Do a full backup before...

Thanks SpeedAirMan!