I forget the socket size, but it's the narrow one (5/8" ?). You'll have to raise the tank and remove the airbox. It's not as bad as it sounds. The only tricky thing is that the plugs are recessed way down deep, so be sure to have one of those long grabber tools (booger puller) with the expandable claw. You'll need it to pull the plugs out of the head after you've carefully unscrewed them via the socket & long extension.
I got the plugs at the local automotive parts store for about $2.46 each. I didn't even check with my wonderful local dealer...