Replace existing domain controller

I have 2 Server 2012, one is domain controller with AD and DNS, and the other one is a file & print server to share folders and printers.

I want to buy a new hardware and install Server 2012 to replace the existing domain controller.

How to export AD users and group policies from existing domain controller and then import them to new server?

Do I need to re-assign the access premission for shared folders (as shared folders are located on another server)?

The existing domain name is jlong.com. If I want to change a new domain name jlong.local, what will be affected in this deployment?

Thanks,

Joe