Having talked to people from the states that have come here I can tell you some things. Nothing will prepare you to the kind of spanish that is talked here, and for two main reasons, we are FAST speakers (almost twice as fast as people from center america, colombia, etc.) and we use a LOT of slang. But don't fret I'm not trying to scare you away; Its's just that sometimes people don't understand that studying formal language doesn't prepare you for the real everyday language. On the other hand I've heard that we have a very nice accent (the famous singing accent)
My first recomendation is that since you know americans living here (or that have lived here) contact them and ask for help, they will know more of the things you should keep in mind (although you probably already did that). Having a friendly place in wich to drop in the beginning can be a huge advantage and they can introduce you to local people.
In the past years we chileans have been over sensitive to cases of corruption (I asure you that it is not nonexistant). Some foreigners (specially from europe and the states) say that we have overreacted, but I believe it a good thing, at least in the sense that it's not considered a normal thing to do.
Check the posts on "Spending a Sabbatical in Chile" and the other move to chile here on this forums, maybe you can find some tips there.
If you want help with a specific topic, just ask.