Is it possible to use the Xserve VPN service without using the DHCP service? I'm working on a friend's network and he's currently got a cisco router handling DHCP. Does the Xserve VPN service require that the Xserve also be handling DHCP?

Xserve 10.6.8
No, Snow Leopard server VPN does not require that the XServe handles DHCP, though you'll likely want to have several IPs on the LAN that will be reserved for the connected device...