You need need to follow the unrecognised NIC article (and if it is an R8168 that article as well, first). Being an MD it needs to boot the OS from network, having the driver in the OS is all well and good, but not much use if your OS isn't loaded! When you are booting your OS isn't loaded, and you need network to do so... catch 22!
The purpose of that article is to modify your MD's initramfs (initial RAM disk) which is bootstrapped by your BIOS PXE software. The BIOS PXE software knows how to use the NIC, so getting the initramfs into memory and running is easy. The code in initramfs is a very basic kernel including all the basic drivers needed then to load the real kernel... so is that file doesn't have a driver for your NIC and the only way to continue the boot is to use the NIC, then the boot process reaches a dead end and thus the kernel panics.