Intranet solution with LAMP (Help Please)

Hey guys, new to this forum.
So here's the deal. I've got exam on thursday and i am completely ****ed. I am supposed to make a presentation about how i can implement an intranet using LAMP. So there's alot i do not know and i'll list a few of them. It's supposed to be a company with 52 employees and they all should be able to have different acess and ****.

-how can i implement an intranet using LAMP (already know how to install LAMP etc, but to make it specifically intranet is what i am asking)
-a plan to make this LAMP intranet secure and with backup
-Securing it with DMZ etc. Where should the DMZ be located and such.
-domain controller with directory service(Like i know i should use Active Directory, but where does AD go. Into the intranet server? Where do i install that etc)

I'm basically sitting here ripping my hair out, like, we've learned just some basic stuff about this. And now the teachers expect me to ****ing make a nett for some buisness.

I can't seem to find any sites where they explain it any good so please help.
All links and tips is very appreciated.