Acquiring 10.8 Server

Question

I am acquiring a Mac OSX 10.8 server from another University and have some questions that pertain to getting on the network while keeping everything running properly.  We have an Enterprise firewall that I have to submit for exceptions.
It is a mac mini running server 10.8 with the following services showing as active: Mail, Calendar, Contacts, Filesharing, Software updates, and DNS.  The owner and group use it as a file server, backup server with ChronoSynch, and to run one person’s Calendar and Contacts (CalDev/CardDev).  May questions are as follows:
1. The DNS service is running.  How do I determine if it is actually being used/is necessary for any app, service or client, or if it was merely on by default when the server was built, and not really needed by anything (like CalDev, CardDev, Mail, File Sharing).
2. In regard to the CalDev/CardDev, if the DNS name/host name of the server is changed, will the calendar and contacts remain intact, where the user will merely have to reconfigure their clients using the new DNS name? 
3. In regard to the Contacts, I read a write up where it says to run Open Directory and have Apple Push Notifications configured.   Is Open Directory Proxy what I need to allow in regard to a firewall protocol exception? [(port 625,TCP(ODProxy) (Unregistered Use)-dec_dlm   Open Directory, Server app, Workgroup Manager; DirectoryServices in OS X Lion and earlier.]
Also, how should Apple Push Notifications be configured?
4. In regard to the Mail service running, I know the users will use our Enterprise mail system but it seems that CalDev needs smtp and imap to send out and receive invitations.  If not using this feature, can one skip this part of the use/configuration of it, or is it needed for other reasons?  Is this a reason to setup and run the Mail service on the server even if users won’t use this feature? 
5. In regard to the Contacts, why would I need to publish LDAP contacts through the service and really, how does contacts/CardDav use LDAP?

Answer 1

So some thoughts
Thanks very much for the reply. To clarify, the server is at the owner's old university and will be moved to our university this week.  I agree that it is better to integrate into the parent environment.  
1. I'll access it remotely to check the IP/DNS situation.  In general, we have enterprise DNS PC servers but with Mac, I am not sure if it is required to run it from the server some reason for the "web" type sockets used for CardDav/CalDav??  Is it?
Ah, huh?  So, at the bare minimum, you are physically moving a device from one network to another.  You will need to, at bare minimum, change the devices IP address.  (This assumes that the two universities are not linked in any way and that you both, by some strange event of the universe, don't have the same subnet).  Now, changing IP address has cascading effects.  In OldU, the server might have been at address 10.0.1.20 and had a name of mac.oldu.com.  This IP and hostname made sense in OldU's network.  When you move the device to NewU, you will need to update the IP address.  Let's use 172.16.10.45 as an example.  When you do this, you will also be changing the devices router address, possibly the subnet mask, and also the DNS server addresses.  The change in DNS is true even if you are using the Mac server to handle its own DNS. 
You have two options with DNS.  The first is to talk to your network crew and have them assign you a fixed IP address for the Mac Server (you will need this anyway) and a host name that they will enter into their DNS system.  Now DNS is no longer needed on the Mac Server.  Recall, DNS is providing identity confirmation.  It is critically important but getting it from OS X itself is no different than getting it from the enterprise DNS service.
The other option is to silo you server so it is outside the enterprise DNS.  The problem here is that you then create an island that can only be accessed by name if you configure other devices with its IP as the DNS server.  This may conflict with resolving other enterprise devices if you are sharing the same name space.  Alternatively, you provide clients with an IP address instead of a hostname, but then the server is useful only on a LAN or via VPN (this assumes that all servers are placed on a LAN behind a firewall in which case a private LAN address in not accessible without NAT forwarding through a firewall.
Bottom line.  You need to change the IP and this cascades to changing DNS.  The server needs DNS to properly function however, you do not need OS X's DNS to satisfy this requirement.  Changing the IP and the DNS will give the server an identity crisis.  Use sudo changeip -checkhostname to repair the identity of the server once you have it where you want it (new IP and a host name figured out).
2. I will have to change the server hostname after all, so in regard to CalDav/CardDav and the user clients currently     accessing this calendar and set of contacts, what will happen?  Where does the calendar and contact data actually live and what steps do I have to take to make sure it is still available to the users and their clients (mac laptop, iOS phone, etc) and what will the users have to do to reconfigure their clients?
Using the examples above... If you are changing the hostname, then the existing users will need to be made aware of this.  If the server's hostname was mac.oldu.com and you change it to mac.newu.com, all users accessing services will need to update their client configurations to use the new hostname.  However, this presents a new challenge. 
Once again, I will assume the server was on the LAN of the Old U.  This means that when users where off the LAN the either (a) used a VPN connection first and then accessed the server or (b) the Old U created firewall rules to allow specific traffic inbound to the server.  This would also suggest that a public DNS record was created, pointing mac.oldu.com to a public address.  For outside users, this request would hit a firewall NAT rule and the request would be forwarded to the Mac server.
Now, if you do not use LAN and instead everything has a public address, then you can avoid this.  I don't know your network so that is homework you need to do.
As for the user data, it is stored in /Library/Server (unless the server data path was modified).  As long as you are not changing the user accounts, then the calendar data remains in place.  The concern here is the GUID values that link the data to an account.  If the accounts stay, then you are just changing a hostname.
Bottom line.  If you change the hostname of the server, the clients will need to be updated with the new address information.
3. In regard to CalDav/CardDav, are you saying that I don't need to worry about creating firewall exceptions for Open Directory Proxy, Open Directory or Apple Push Notifications?
Once again, not sure how NewU implements servers.  If the device is on a LAN, then a firewall rule will be required to access the CalDav server.  For this, you do not need to allow access to Open Directory (this is LDAP).
oops - got to run - that's a start
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