I had the same problem with the audio patch files myself. If you look at the code in the i810_audio.c file you can see the place where the patch should probably go in, but it doesn't exactly match the diff output provided by nVidia in the .patch file. If you change the patch file's context lines to exactly match your i810_audio.c it should install without any problems. I haven't been able to test sound output yet because of my lack of network and not being able to retrieve a sound player program, but it appears to be loading up properly on bootup and lsmod lists it.
If you need it, I can post my patch file tonight when I get back from work. I don't see any reason it wouldn't work with Sarge as well as Woody.