If you are using cgminer you shouldn't need that much ram, I had 4gb on a previous rig running 5 cards.
You should not need a monitor after you set up the bios (Power on after AC loss and boot from usb).
You can view the 'screen' from your normal pc, if you are using windows 7 you can just use remote desktop connection from the start menu to do all the configuring.
To power on initially don't worry about a button, just short the two pins on the header with a screwdriver, after this set the bios to power on after ac loss. This means whenever you turn i on at the wall it will automatically turn on. Or if there is a power cut as soon as there is power you are back up and running.
Bamt will just mine to any where you tell it, if you want an auto switching feature look at pools that offer it such as hashcows.
As for the alarm, most decent mining pools will have that function withing your account settings, sending you an email after no activity is detected.
The cpu will probably not have paste on, but the heatsink might. take a look at the bottom if it just metal you have no paste, if there is a square of paste you are golden.
Any more questions feel free to ask.
That's what I thought about the RAM... looks like the Frys guy try to oversell me LOL.
For turning it on without a power button, where is the header on the board? Near CPU?
Thanks for the rest of the tips, they really fill in the gaps!
EDIT: Figured out the power button thing,