Hi all

I have a wireless internet connection from an ISP and my office clients are at least 20 PC's. I'm routing internet connection through a Linux server. and for this i'm using static IP address because i also need all the PC's accessing from any machine.
1. My question is that, if i want to configure DHCP in my Linux box, can i
accessing all machines from my LAN?
2. Can anyone tell me the full configuration step of the VPN in Linux box?
3. Suppose there is no DNS running in my Linux gateway Server. If i want
to configure Qmail as a relay, if it's possible?

I'm also want some links related to the above.
Thank u all.