This should be relatively simple. You can easily create a new subnet, VLAN and SSID alongside the old one to configure, test etc. Then for cutting over users, you can either have them manually connect to the new SSID, or use GPO or an MDM software (Meraki Systems Manager, Intune etc.) to configure the new SSID on each machine.
I would transition some key test users over to the new SSID first and make sure it's all working, and once you're happy with it, push out the network settings to all computers and turn off the old SSID.
The approach will probably depend on the number of users on the network, its importance to the business and whether all connected devices are managed or not.