While that should work, Z-Wave replace can be a bit finicky in my experience. I would suggest pairing the new device like normal, using Swap Apps Device to switch them around, then doing a "Remove" from Z-Wave Details on your old device (or a proper exclusion if you can, but it sounds like it's too late for that).
This will work as long as they are both just regular devices (no child devices), which it sounds like they are.