Torbar, besides the Quicksilver, what other Mac did you want to hook up?
What you are attempting to do is possible. I'm assuming you have either DSL or Cable modem as your connection to the Internet for your Quicksilver, right? If so, you would need to treat the PMG4 as a bridge or gateway for Internet traffic.
You will need to forward Internet traffic through the modem port and set up a static IP address on the modem port. Then you will need a standard phone cable to link the 2 Macs together. I am also assuming the other Mac has a built-in or external modem. Also, make sure you have AppleTalk enabled on both Macs. If they don't connect right away, try restarting both machines until they do.
Before I go any further, I need to know the details of what other machine you are using and the OS version.
73s 8)