Yeah Near Infinity is what I'd recommend, it's a lot faster to compile and get your scripts working with it because it can look at the scripts in BIFs and edit them directly. Then you can save them to override etc. all in the same program. Also, with NI you don't need to worry about BAF (source scripts) files cos it decompiles BCS files automatically unlike other programs.
Anyway, any questions you have are likely to be quickly answered in teambg scripting section or you can post them here and I might be able to help...although there are more people there who can script than here
The AI in the game is indeed crap and it is very easy to make some improvements but very difficult(impossible but we could get close) to actually make the AI look like a human is playing.