really there is no definitive How To guide because all hardware is different all I can say is do some research on different Snow Leopard discs and choose one that has most of the kexts that match your computer's specs burn it to a disc and boot from it and see what happens the hardest part is getting it to boot after it's installed and since you know how to use grub that should be simple. Once you find a modified SL Disc it should be easy to get it going cause once it boot's its all a guided install from there If you get stuck at a certain point just ask for help.