Maybe, no and no. By main gasket, you are referring to the front crankshaft seal, maybe? You could replace it or you could leave it alone. Leave it alone if not leaking. If you decide to replace it, look for a Youtube video or forum thread on re-sealing the oil pump. BTW, the time to remove the old crank gasket is when the oil pump is off the vehicle.Do I need to replace with the main gasket and the coil gaskets, also the half moon gaskets that we have or we don't have....?