instal us atlantica. copy almost all the lang folder content to your spanish version. exception the patch info in the ENG subfolder of LANG. also everything that has eng in it's name has to be canged so it has esp or whatever shortcut for the spanish files you have. Also the ENG folder will be renamed in esp (or which ever is the name of your language folder).
This should work. Us Total commander for mass renaming.
last post is from may so don't download that file, it's outdated for sure, just read the instrucions.