So your FedEx stuff is working correctly for you? You are getting an error with the checkout? What is the gateway that you are using? Have you configured the checkout wizard to use this gateway? If you have questions about any of the specific values that are being requested in either the wizard or the local checkout server behavior clicking on the help button on that page should take you to the help content that is specific to that page. This should clear up any questions about what values are being requested from you.
If you continue to have problems please post back and include some additional details about your setup and what you have tried that is not working for you. It might be better to start a new thread if this is a new issue. A new thread would probably get some more interaction on the forum as this one if getting large and might not be seen by others.