UK JAA to FAA. I did this a short time ago.
Some or all of the following is open to correction, so sorry for any errors.
You can download the test question bank stuff, as an alternative to the CD.
For a fee.
In the UK, you can take the exam at FS Farnborough, at £70 a shot, If I remember correctly. If in the US, the FAA website gives a list of test centres. All ATP for example ( I think), for a better dollar amount.
I did it in the UK for expediency.
Pass is 70% I think.
You have 2 choices, Part 121 exam, or part 135(?)
I chose 135, but in hindsight, I should have gone with 121.
exams are mixture of questions. 135 exam has performance, loading questions on something like a small commuter TP. 121 would be more akin to A32x/B737
You get a snazzy little credit card, but privileges are available on completion of a flight test (light aircraft, etc) or completion of a FAA type rating. I did the latter. You still have to do a course, if I understand correctly, even though you may have a JAA rating.
eg.JAA B737 rating, and 1500hrs on type, you can do an experienced airman (short course) to get the FAA rating. You are not automatically awarded ratings.