|You don't need a router. A simple 8 port switch will do nicely.|
You will need regular patch cables to connect all PC's to the switch. You can't use the crossover cable as it's only required when connecting like devices.
I haven't used ICS in ages but if memory serves me, the IP address of your "host" ICS computer will be 192.168.0.1 with Subnet Mask: 255.255.255.0
Your second computer will likely be: 192.168.0.2 with SM: 255.255.255.0 and Default Gateway IP: 192.168.0.1
To add your Mac you will give it the following: