Server - VPN, Calander Sharing, Network Info Questions... HELP!

Hi everybody. I am in a bit of a conundrum...

I have been elected to setup our server here at work (small business). We have 6 MBP's and a Mac Mini as workstations, and we use another Mac Mini running OS X Server. We also have a Time Capsule for backups, etc.

I have spent alot of time looking this stuff up, and have places several calls to Apple support... and I'm not exactly getting clear answers.

My End Goals:

1) Setup the Server with Network users

2) Create and Share server based Contacts list (sales list for our purposes) and Calander sharing

-Users must be able to add/edit to the Calendars and Contacts... would be preferable if permissions could be set

3) Enable a VPN connection so our files, contacts and calendars are accessable if a employee were to take their workstation home over the weekend.

I have spoken with Apple 3 times, and have gotten conflicting answers. To start, our network is all local users, not network. I have been walked through switching local users to network users, and believe that isn't too difficult. What is confusing and frustrating me is the order in which I am being told to do things. My most recent Support call resulted in a lot of questions about how our network is setup (on the side of our ISP) having to do with port forwarding, DNS and what kind of IP I have.

I was going to make the network switch, Enable Open Directory DNS and Contact service, up until the point where Apple saw that our router may be controlling aspects of our network. I was told that in order to make future changes possible (for example, enabling the shared contact service one week then setting the VPN up later) I would need to get some more information from AT&T about our service.

I am looking for some clarification on what exactly I need to get this set up right, and if anybody has a similar setup or experience. It shouldn't be hard to share Contacts between computers connected to the same server, and it shouldn't be hard to enable the VPN connection. It is difficult to set this up and know what I'm talking about when Apple techs keep giving me different stories.

Can anyone shine some light on this for me? Thank you very much in advance, I REALLY appreciate the help understanding this. With every day passing, I am learning more and more about Apple and their products, and I don't want to become disenfranchised with the brand. Def missing exchange functionality at the moment!