Motherboards have a protective layer over the traces which make it much more resistant to slight nicking and shorting, usually hitting it with the screwdriver while installing the heatsink isn't too much of a problem (unless you REALLY smack that sucker), so don't pee your pants over it. But damn, I really want to smack the guy who thought of that dumb clip retention system up. The P4 retention system is so much better. Faster, safer, and it just looks cool.
I use plain old screwdrivers, I tend to use the thinnest ones (not necessarily small, just a thin tip). If you can get one that fits just perfectly, slapping those heatsinks on becomes much easier. Note that if you use thinner ones, that means the screwdriver has a sharper tip, meaning the chances of messing up your motherboard are greater, so you have to balance between too thin and too thick (you don't want one so small it goes right through the little nubbie thingie anyway).