Gary, I am presently doing OS X/OS 9.2.2 file sharing over an Airport. All is seamless, even simultaneously accessing the broadband cable modem. As long as you have the same or compatible applications on both machines, the files will open as expected.
The only "gotcha" is that printer sharing between two different OSs is not (yet) doable.
Regarding needed equipment, most any router/LAN/WiFi system will work, but as I am only familiar with an Airport network, others can better address the specifics.
Harv
[ 02-26-2003, 01:24 PM: Message edited by: pendragon ]