I will also be installing on my office intranet if I go ahead, so may I ask whether "internal hostname" means the name given to the apache virtual host for aC? Should this be the internal FQDN (achost.office.example.com) even though it doesn't appear in public DNS, or just the hostname?

What would happen if at some point in the future I wanted to open it up to external clients with a public DNS entry (achost.example.com) forwarded through the firewall?