Tutorial [Q] How to add local language or character to rom

Dear Friends,

I have a Galaxy 5 (GT - I5500) rooted with froyo 2.2 and I want to use Persian (also called Farsi, similar to Arabic) texts on it.
I have installed Go Keyboard and its Farsi language pack, but as the characters do not exist in my device, I get a "square box" for each character.
Is there any trick I can do to introduce new language or new characters to the Rom?
Obviously, I'm not going to replace fonts, this has to be something far deeper.
Your help and support on this is highly appreciated.