Ip address change

I was asked to chage my internal IP addressing sheme by my local ISP (we have multiple outside IPs that are conflicting) How do I go about changing the scope (ie from 192.168.x.x to 10.42.x.x). I’m also wanting to place my dhcp server on a differentmachine. Wouls it be best to build the second machine, install and setup DHCP on it with the new scope, shut down the original DHCP server, install the new DHCP server ,re-boot the network? P.S.I’m running AD. Thanks in advance