I don't know about the sound, but the video and lan can be fixed by going to www.nvidia.com's website and downloading the linux nforce drivers.
The PITA is of course if you can't use the lan, how are you suppose to connect to the internet to download the drivers? Well... That's why I sold off my nforce2 board and bought a via kt400, which is infinately nicer for linux.
But non-the-less the drivers for Nvidia do work well and are well documented.