100% agreed on the Certification Manual. That's really the only book I studied prior to the seminar and testing. Get you code book also and get really familiar with it.
Here's some idea as to what is on the test: Definitions (according to AWS 3.0); heat control and metallurgy (you better know you metallurgy); reports and records; welding processes (covers all processes, not just SMAW, GTAW, GMAW, FCAW. it includes the lesser known ones too like PAW, ESW, EBW); NDT test methods (know your NDT and the fundamentals behind the 5 major methods); Destructive test (you had better know about ductility, brittleness, tensil strength, yeild strength, elongation and what test methods check for what); symbols (you better know all of them and be really familiar with them and their applications). You had also better be prepared with inspecting to a code for your practical, and be familiar with actually inspecting. Most people retesting when I was there were there because they failed the practical part.
As for calculations and formulas...that's the easy part. They give you all the formulas. It's simply figuring tensil strengths, and converting from one unit of measurment to another. But, as I said, you have access to all the formulas.
I highly suggest the seminar. It helped me realize where I needed to improve my studies.