97 nissan maxima throws a multicylinder code and throws white smoke?

You have either a blown headgasket, cracked cylinder head or an intake leak (if its a v6). the white smoke is coolant getting into the cylinders and not burning with is causing the misfire code. Being that its a multi misfire, Im guessing its a blown headgasket. this causes a chain reaction of codes, like the O2 sensor, which is ruined by now, and knock sensor codes. The water in the cylinders if it is enough is trying to hydrolock the engine which is probably being mistaken for spark knock by the knock sensor. It can also throw rich and lean codes as well. Pull the dipstick and see if its a milky brown color yet. There is no cheap way out of this one I hate to say.