Arcanum modding is much livelier today then one could expect for such an old game. Here's a bunch of tools by which the task of creating complex quests and populated towns becomes less tedious. Feel free to go to the forums to clarify all your doubts regarding the use of these files. And if you don't know where to start - check out AMTUT.
Arcanum Modding Tutorial (AMTUT)
by DarkUnderlord
If you're new to modding Arcanum, AMTUT is where you should start learning how. This step-by-step tutorial goes from the basics to creating complex quests and alternate endings for your module. Also availiable online