I am attempting to come up with a way to create the following network

3 remote offices with 5 computers in each.
1 central server with 25 computers.

I need to set up a Firewall, Secure VPN, a mail server, a web server,
and a news server, and possibly a chat server at the central office.

At the remote offices, I need to set up firewall and VPN router ... to
connect remote office to central office, to get user authentication
and to access files and e-mail ...

has anyone ever done this ... I am sure someone has ... but I have a
real short time frame and not much infrastructure capital to put to
this project ...

I am not trying to milk everyone for free .... but I really need some
help ... even if it is a list of software to use ... I just need a
starting point to run from..