[badbadbad]

What module/script do I have to install?

For starters, you might want to look up some video tutorials on how to implement an OpenWRT wireless bridge.This might solve your basic problem in connectivity.

Now regarding custom scripts (logging into WiFi web portals, creating Guest WiFi, etc.), I can't help you per se, but I always head over to the forum in this place as they have a few DIY scripts and a very helpful community.

Hope this helps.