The GA-K8N uses a 8053 Marvell Gigabit Ethernet controller. You can use the 8053 driver supplied by Asus if you want to get it working (for example here
The NForce4 USB subsystem is an USB2-EHCI compatible one. The EHCI HCD driver of the standard Linux kernel should be able to manage it. Notice that the 2.6.10 kernel introduced a workaround for another USB chipset that conflicted with some NForce4 revisions, so if you don't manage to properly detect any USB peripheral connected, try with a 2.6.11 instead.
Hope this helps !