Hi
You can directly update configuration files, and at least restart the listnener.
%ORACLE_HOME%\NETWORK\ADMIN\tnsnames.ora
[...]
(HOST = 1st_host_Physical_name)
[...]
%ORACLE_HOME%\NETWORK\ADMIN\sqlnet.ora
[...]
(HOST = 1st_host_Physical_name)
[...]
Also make sure that if instance parameter "local_listener" is set it is using physical hostname.
Regards