Fate XP3 Files

I'm painfully new here as well as to this whole doujinshi/hentai/visual novel, or whatever the heck you wanna call it, scene.

I like to extend a special thank you to Ed from insani for pointing me in the general direction of getting started, quoting programs that I'd find useful and well as some hints and a link to this forum. I need some more help.

I've been a fansubber for several years and a friend of mine (that works with me in the group I'm involved with) is working with a fansub group that's subbing the Fate/stay night anime. With this prospect, I asked if they also might want to translate the game as well. It would be good for them and it would also give me practice in order to learn how this all works, but I've run into another snag...

I have no idea how to write a repacker for the Fate XP3 files so I can pack the translated scripts back into it. I've looked online for tutorials on how to write packers, but I couldn't find anything beneficial to my cause in a language I have tried, and am still trying, to learn during this whole game translation process: Python or C++ (preferrably Python which is a language I'm more familiar with than C++, but either is acceptable).

What goes into writing a packer? How does the XP3 compression format work? How do you figure out how a file is compressed in order to write a packer/unpacker? Is there an easy way to learn these things?

I'm not asking for explicit instructions or a step by step tutorial, but maybe an example, a link to some place that would be helpful in learning, or the source to another, similar packer so I can get an idea of how one works...

Before Ed at insani replied to my e-mail about getting started, I've asked others before him and I've been flamed and called a stupid idiot, so I've not had a very good track record with asking questions about this subject (and am ultimately afraid of asking such questions, but with the abuse I've sustained I've stopped caring at this point).

On top of it all I'm a slow learner and it takes time for me to understand this stuff... I hope someone here can help. And thank you.