1 - Nope, just be sure that if your ASUS board is set to IDE mode for SATA, that your GIGABYTE board is set to IDE too. If the Gigabyte SATA mode is set to AHCI, boot up, change the registry entry to allow AHCI and then switch it in the BIOS. There's a guide
here2 - Yes, the guide on the plug should line up with the socket. There's like a ridge on the back of the fan connector. The 4th wire is the sense wire, which tells the chipset how fast the fan is going so it's not needed.