To change the cell name for a given environment, use the following wsadmin command:
This updates your configuration with the new cell name you specify and will optionally regenerate the certificates in that environment.
To change the name of a given node, use the following wsadmin command:
This updates the name of the node specified by the nodeName parameter to the name specified by the newNodeName parameter.
To change the host name for a given node, use the following wsadmin command:
This updates the host name for the node specified in the nodeName parameter to the value specified in the hostName parameter.
These commands update all of the necessary WAS configuration, but do keep in mind they do not update any shell or batch files in the environment. This means you need to update the setupCmdLine script included in your WAS installation, and you obviously need to update any of your custom scripts that have hard coded values for cell, node, and host names.