how to replace oil sensor in 1995

If you have smoke coming from under the engine covers, why do you think it is the oil sensor? It more that likely from the information you gave, is an oil seepage from a worn gasket, probably from the valve covers or intake manifold which is a common area for leaks. The oil sensor sends information to the engine on the pressure the oil pump is putting out. Now that could be a source of the leak, but before dropping a 1 1/16 deep socket on it, make sure there is oil around it, and it only. Trace the source of the oil going to the exhaust manifold before throwing money into what does not need fixing.