Hi
As long as the Clusters are in the same Datacenter (vCenter Datacenter), you do not need to reconfigure DVS.
I did host & cluster movement / break for a couple of times before in a production environment.
The steps are:
1. Create new cluster in the same Datacenter.
2. Perform maintenance mode on the hosts that will be moved to new cluster.
3. Drag and drop the hosts from old cluster to new cluster.
4. Perform exit maintenance mode on the moved hosts.
5. Reconfigure HA Admission Control Policy.
6. Migrate or vMotion VMs as necessary
You do not need to configure DVS if you are planning to use same VLAN on those 2 Clusters.
You can also perform cross-clusters vMotion as long as they have access to same shared storage but you will need to enable EVC if they are belong to different CPU Series.
You can check the EVC/CPU Matrix here http://www.vmware.com/resources/compatibility/search.php?deviceCategory=cpu
Thanks,
Bayu