fungus:
b) You can replace an ATmega328P (the chip on the Arduino) for about $3, and they're quite hard to destroy, read these forums for examples of the abuse they survive...
Not really a precaution, but a bit of pro-active planning: order a couple of ATmega328P with the Arduino bootloader on them. That way if you do take one out (or an IO pin), you can swap it and move on.