Wireless Network VPN to Secure Wired-Lan

Can anyone point me to any good how-to's on how to set-up up a VPN
between a wireless network and wired lan? The wireless network is
basically just an access point and any wireless clients connecting to
it. There is no internet connection .. that is all controlled via the
wired lan.

I picture something like this:


wireless-client --->
access-point---(wired-nic2)--VPN-SERVER--(wired-nic1)---LAN
wireless-cleint --->

the clients would probably be winXP..the VPN server I am leaning
towards openbsd or linux. What I can figure out, is what provides the
DHCP for the clients once connected to the VPN..does the VPN take full
control of all the traffic?

Thanks