Integrating third party payroll with Projects

I am working on a project to use payroll calculated by a third party for project costing. The documentation is not clear on a few things:

- If we're using a third party payroll, is it required to set up payroll elements in HR/Payroll, or are the values defined in the Third Party Pay Elements lookup all that are required?

- Is the Projects and Payroll TImecard layout required in OTL to integrate a 3rd party payroll with Projects?

- Where is the 3rd party payroll file loaded to be used by the PRC: Process Payroll Actuals program to use?

- How are the values defined in the Third Party Pay Elements linked/mapped to the 3rd party payroll file?