My wife and I adopted a child from China last month - we were given a packet of information from the US consulate in China and told to hand it unopened to US immigration as they would process the paperwork upon arrival, we waited about an 1&1/2 at LAX to be processed. Our daughter received her permanent resident card about 10 days later :-). Not sure if the situation is the same but sounds like it could be - was pretty straightforward though, good luck :-)