No, you don't need to patch the kernel for agpgart. The nVidia graphics driver includes a kernel module that can either use agpgart (if present and working) or it's own builtin functions. By default it will try agpgart first (which will fail on the nforce2 chipset) and then successfully use it's own functions. If you want to avoid those warnings from agpgart you can set an option in XF86Config that will tell the nvidia driver to always use it's own functions (It's in the README).
It may still be a good idea to install the kernel-source package even so you could get away without it.
When you boot SuSE specify acpi=off on the boot command line (otherwise the 3Com NIC will not work properly).
I'm using both NICs and they seem to work equally well (most traffic goes through the nvnet interface).