In my House every outlet is a 2 prong plug in. I want to replace them with 3 prong. There is no place to connect the ground to. My question is can I attach the ground to the outlet box that is nailed to a 2x4??? Or do I need to run a seperate ground to every receptacle??? All the wiring is in good condition and no problems with any overloaded circuits. Also how would I install aGFC in my bathroom ???