SIM card comes right out. No hammer needed.
But if you really have an urge to take one apart here are the pics.
http://thinksecret.com/archives/iphonetakeapart/
It's ATT that has made this the most locked down phone ever. Even SIM cards from other ATT phones do not work in this phone.
Since the phone is locked in software I'm guessing that it will not be long before someone finds a way to hack it and unlock it.