Hi, did you transfer the DNS already? Remember that you need to transfer the DNS zones to the new server in order to let the users resolve addresses correctly.
Please refer to this article that explains the process
Also reconfigure your DHCP settings. You need to update the DNS server IP address in your DHCP server.
You also need to make the new server a global catalog, and probably transfer some of the FSMO roles to it as it is more powerful hardware.