Like everyone with a SOHC, I'm still looking for my PCV valve. I've found where the two horizontal hoses come together at a "T" with a vertical hose, so I assume that this is the PCV valve's location.
Regarding changing the back spark plugs, I pull both front tires and go at most of the plugs through the wheel wells. It's still not particularly easy, but at least you have access to all of the spark plugs.