You cannot officially translate XMPlay (yet). There was a Russian hack floating around, but how it was achieved wasn't revealed. To skin XMPlay you need an image editor and a text editor (notepad will do) to modify skinconfig.txt but you can also generate it with XMPlaySkin
(although the current version doesn't support all the new features the skinning system now has). There is some help at the Support Site
and you can download the Skinning kit
to get you going. I'm taking my first steps with skinning too at the moment, and I can say the best way to learn is to look at other people's skin sources or even start by modifying them. You can download many skin sources from the Support Site.