I think it won't be the case. You see, GIGA's most commonly used engine is NeXaS. But the topicstarter said this game is on Artemis. And it uses pfs archives and .asb, .lua and .AST scripts, so this engine is most likely Artemis. So even if people know about working with Artemis games, they could work with only few games of GIGA.
But I have worked with Artemis at some point, so I'll post here a method (do note, there are some other methods as well).
1) Extract archives with GARbro (there are some other tools, but GARbro is the most supporting, for there are some types of pfs archives). You need to preserve the folder structure.
2) Change font (if needed). Most often it in "font" subfolder from archives.
3) Edit scripts (strings in scripts or actual code). Scripts are in open format (well, it is case in most Artemis games at least), so there should not be any problems. It even uses Unicode (as I saw).
4) Edit images. No problems with this one.
5) Delete archives to force game pick data from subfolders.
That's all. NeXaS is somewhat more tricky, especially then working for non-English translation project.