I think you are freaking yourself out with the unknowns, but this is really easy. Do you know where to find the network setup wizard?
Plug your cable in to connect the two computers.
Run the wizard on each machine. Answer the questions the wizard asks you about your internet connection (if you have one), give each computer a unique name, making sure to use the same workgroup name on both machines.
Once the wizard is run on both machines (and the cable is connected), the machines should be able to "see" each other in My Network Places.
Enable shares on whatever drives / folders on each machine that you want to give the other machine access to. These shared folders will then be visible in My Network Places on each machine. (Do you know where to find where you enable shares?)
You don't need to worry about IP addresses; Windows will handle that for you (unless you have special requirements where you care about the IP address).