File swapping -- you need to start the Networking Wizard and follow that. But make sure to turn off Windows or other firewalls on the machines while setting up. Make a note of the computers' names (Control Panel, System).
Enable file sharing in the relevant folders on both machines. Go to My Network Places, Add a Network Place (and go and make a nice cup of tea to calm you during that process as it's sometimes quite pedantic and slow, thanks Microsoft).
I would also advise doing this initially with the computers linked by ethernet not wireless (either a crossover cable between the computers or straight-thru cables via the router)
Printers ? -- figure those out later once you've passed your baptism into networking.