What are the steps that need to be taken when changing the IP address of the Policy Server?
You need to start the web agent otherwise if the IP addresses of the policy servers are changed before agent is restarted then agent won't be able to connect to the policy servers.
NOTE: Best way will be to modify the SmHost.conf and HCO with the new IP addresses of the policy server then change the IP address of the policy server and then restart all the agents.
Dynamic HCO is supported started 6SP6. If webagent is configured to use Dynamic HCO then after modifying SmHost.conf and HCO there is no need to restart webagent. Changes will take affect dynamically.