Chuck,
AWS has a set schedule for the exams. You will have to look it up and see when they will be in your area again. I have a guy that took the exam when I did, He failed it. He went to Knoxville, TN to retake it, but failed it again. Anyway, I know that they schedule Knoxville, TN sometime during the year. The prep course that I took was held in the same Hotel that the exam was given in. (Mon - Fri was class and Sat was exam.)
I took the D1.1 exam, but it's really up to you which exam you should take. The prep course will be D1.1 oriented. The guys on this BBS have various opinions about which exam to take, all of them have valid points. Look back through some of the old posts on this topic and read them for a better understanding of what I'm speaking of.
Which ever code you choose, you will be able to interpet either code, provided you pass the exam. The CWI certificate does not have any code listed on it.
I wasn't trying to scare you telling about my employee's failures, I just want you to prepare yourself before you go take the exam.
Hope you fair well on the exam,
John Wright