Zulu,
Have you talked to the training center you're going to? They'll have to ensure the check airman is authorized to issue an ATP. And they should be able to help with the background check and verification. I don't know if anyone does a traditional ground school for the written test anymore, most folks complete an online program. But you will need to complete the ATP Certificate Training Program before you go for the written. It does almost nothing to prepare you for the written test but is a requirement. If you are going to CAE at DFW they are authorized to conduct the CTP. ATP Flight School has a branch near DFW too and they also conduct CTP classes. Their class fee includes an online written test training program.