Six: two to screw in the bulb and four to testify that it was lit from the moment they began screwing.
None; the bulb will change itself when it is ready.
Four. One to change it, one to sing about how heartbroken he is at the loss of the old one, one to sing about how madly in love he is with the new one, and one to go "Yee-Hah!" and throw his cowboy hat in the air.