Friend is an arduous but very rewarding path. I'm already finalizing a translation into my language, which is Brazilian Portuguese.
Well, for starters I highly recommend you to use Mod Moguri, because with it you can extract all the texts in the game. The best part is that you can translate simultaneously with the game open dialog by dialog. So you translate from English to your language and re-import the texts into the game.

But there are texts in images, in which case you need a tool to extract these images, edit them to your language and reinsert them in the game.