I dont know who to change or programs to do it, but if i know how to do it, i could translate all to spanish.
♥♥♥♥♥♥ great mods guy, i love you :D

Hi Muehehehe! Making a spanish translation in very simple!
Follow these few steps:
1) You need Pack File Manager (PFM) program and you can download it from Total War Center:
http://www.twcenter.net/forums/showthread.php?730823-PFM-4-1-2-Warhammer-support
2) With PFM open my english o italian translation pack file. Under text/db/ folder you will find some other file with different name; then you can start to edit the english or italian strings (on the left) with your in spanish.
3) Once you have finished the translation work save the pack file with the name lore_friendly_units_buildings_language_pack_spanish.
4) When you have finished I will give you the mod icon with spanish flag and then you can upload the spanish translation mod.

Thank you for your appreciation and I will be glad if you will be able to do a spanish translation.
Cheers!