How long customs takes depends on how many other jets arrive at the same time and how many people they have working. It could be 20 minutes, it could be 2 hours. (I suspect the former is more likely, but I'm still bitter about the time it took me 2 hours). The airport's quite small, however, so once you're done with customs you're basically out the door.

As for clothes, check the weather online and pack accordingly. Or is there some hidden meaning I'm not getting?