the airport extreme base station will do all that you want , it will dial up and share that connection wirelessly and with the usb port it will share a usb printer with all computers connected... if you don't need the printer to be connected to the base station like you have it connected to the desktop you can use the "snow" base station to share the modem connection and if you leave the desktop on and connected you can share the printer by setting it up in os X with an ip address (this is the setup that I use) it works great!!
my setup is as follows.. 12"powerbook airport extreme, 14" ibook airport, and my 3 year old sons celeron 1gig with a netgear usb wireless adapter all connected to a d-link di-614+
wireless router connected to a cable modem
oh and the printer is connected to the 12" shared with the rest wireless..
(I do have a snow base station not in current use wanting to sell or trade up for the airport extreme with usb port)
good luck
Bill
