Opening a fract T1 for modem access in Linux

[Jared]

I am purchasing a fractional T1 which I want to allow users
to dialup and use. I will also be using it for a local network,
and am getting a fracT1 because of its scalability, rather than
a cable modem. At this early point, I am open to all kinds of
suggestions on how best to utilize this small pipe. I think I can
find my way around getting wireless access into to it, once it
"greens up" in late October.

My main question, after visiting linuxdocs.org and browsing
through several HOWTOs, and after searching Google and
finding thousands of pages on how to dial IN to a server,
but none on how to set up such a server, is:

What is the best way to set up a box which handles firewall,
dialup access, and local network access to a T1?

Thank you to all who can help me.

-Jared

p.s. the T1 connection will be 6 blocks from the downtown
K.C. Public Library, so it will be convenient for KCLUG to use
if ever the need arises; should be able to broadcast a secure wireless
signal that far... More info as it comes available.