Hi,
I took the CPS class last November. It is a fantastic class! An overview - there is a 36 hour class that you take. During this class you learn all about car seats - their use, selection, parts, limits - as well as crash dymanics, seat belt systems, and other things. Part of the class is lecture, and part of it is hands on learning. There are several "hand's on clinicals" that you have to pass. Then you participate in a free car seat check clinic at the very end. They are held in various places. Mine was held at a fire station and the state's coordinator had a grant to cover the expenses so my class was free. I have also heard of some classes costing only $10, and other's costing as much as $100.
As Darren said, contact your state's coordinator and he/she will send you in the right direction.
Best wishes,
Sara