DNS and Domain Controller network

Need to configure DNS and Domain Controller Services in Linux. The linux server should act as a Domain controller for about 50 PCs using Windows XP / Vista/ 7. Also there are a couple of other PCs running Windows Server 2003 and Windows Server 2008 and they should be able to join this Domain. This is going to be a Domain Controller for a LAN behind a firewall, it is not going to be out in the internet, however all the security measures should be taken. We use all kinds of folder sharing by user permission, authentication, so basically we would like it to work as a Windows Server Domain Controller. We have heard Samba works for this, we don't know the details. We would provide a basic linux installation for the job, you can suggest which version works best, we would like your advice on whether this Domain Controller should be installed on a physical PC or if it can be a Virtual PC We would need a basic instruction manual on how to add/edit/delete users and PCs in the Domain, and any other thing we would need to know about the Domain Administration. You should be available for support by Messenger and Skype in any case we need to contact you in the next weeks after the job is done. Previous project experience is a plus for selecting freelancer.