If you are already using the DHCP service, then no you can't turn on ICS. ICS wants to have it's own little DHCP service running, and it will conflict with the regular DHCP service. Setting up routing and remote access (RRAS) is really straight forward. Just run the RRAS mmc, and use the wizard to setup NAT for internet sharing. Once that's done make sure to take the time and turn off the every service on the Internet connected NIC, except Tcp/ip. also you should put in some filters (use rrras or IPSEC for this) to stop ports 42,135,137,139, 500 from working at all on the internet connected nic.