Hi Sting! Well I hope I can solve this problem of yours in a simple manner. Here we go.
First off, a crossover cable is an ethernet cable which can link two computers and two computers alone. It is known for being a quick, cheap, and easy method of networking two computers.
However, in your situation, you have three computers. So in this case you needs whats called an ethernet hub. This device allows more than two computers to be networked at once. This method is the easiest way to network multiple computers. Hubs are usually priced at anywhere from $20 to $100 american dollars. The price depends on the amount of computers the hub can connect and the speed of the hub. For speed, aim for a 10/100BaseT hub, they are fast and most common available.
Now about networking the computers, well you did say that you are strong in the MacOS so I will leave it at that you know what to do. But for the peecee, I would wait for someone with experience to help you out there.
Here are some links that will help
http://www.macledge.com/netgames/network101.html
http://www.macledge.com/netgames/networkFAQ.html
Hope this helps ya!
------------------
"I drank what?"
-Socrates