HeliEC135,
There is no FAA airlaw exam.
As far as flying over here goes, you'll need an FAA license which you can obtain on arrival at the local FSDO (assuming you've gone through the foreign license verification process).
You do need to do a flight review with an FAA CFI prior to being legal...minimum of 1 hour of ground and 1 hour of flight. After you get signed off, you'll be good to go.