As for RAID setup, I have personnaly done it both ways, it does not matter which drive is first. However for your information, Drive 0 is the right drive, Drive 1 is the left drive as looking at the front. When you insert a second drive the system will realize it and ask to format it. Then you have the option to place it as a RAID 1 if you like.
I would recommend that depending on how you use the NAS, you should think of placing it on it's own UPS for backup power. I have one that I hope will last about an hour with the drives pulling all 18 Watts while running. I have my drive set to power down after 30 minutes of inactivity.
Just an idea worth thinking about.
-Joe