You're making it sound complicated.
Get a Router/Lan HUB and stick all 3 lan cables in the "Downlink" port of the Router/HUB (if your cable is crossover, put it in uplink. if you dont know if the cable is crossover, put it in downlink and test it). After you stuck 3 network/lan cables in there, stick the other sides of them into a LAN port (just look at your computer, you should find it). A light should turn on. If it doesnt, maybe you put it in the wrong port on the HUB. Now restart all your computers, and see go to "My Network Places" (if you have XP). Then click Workgroup computers and see what computers can see who's. If there is a computer who cant be found or cant find anyone, they have to do the Manual IP thing (i think dell_ate_my_dog tells you that, if not, someone will i hope). Then you're done.