In the 10 years Ive spent assembling or dissasembling PCs both at work and at home, Ive yet to kill a working component with a static shock. If your really worried buy a wrist strap.
Dust does hamper the cooling in a PC - but not by much, it needs to be several milimeters thick before it causes it to loose more than 1 or 2 degrees worth of cooling.
A good practice is -once a year take you PC outdoors (when its not raining
) remove the side panel and hose down the guts with can of compressed air, remove the cpu fan and blast the heat sink and fan clean too, also wipe off any thermal compound and reapply some fresh.
Its worth removing the graphics card so you better clean out the fan on that also,
A compressed air duster is about 5 euros or so and it should last for ages if your only using it on one machine.