The oxygen sensor may be difficult to remove when the engine temperature is less than 120°F (48°C).
Remove the exhaust manifold heat shield.
Disconnect the oxygen sensor harness connector.
Remove the oxygen sensor using the oxygen sensor wrench, J 39194-C.
Coat the threads of the oxygen sensor with anti-seize compound GM P/N 12377953, or equivalent, if necessary.
Install the oxygen sensor. Tighten the oxygen sensor to 22 ft. lbs. (30 Nm).
Connect the oxygen sensor harness connector.
Install the exhaust manifold heat shield. Tighten the heat shield studs to 16 ft. lbs. (22 Nm).
Note: it isn't hard to change the O2 sensors, just like changing the spark plug. Local auto parts stores such as Autozone or O'Reilly have a free loan tool program and they have the O2 sensor tool remover in stock.
For additional information, see this ... http://www.autozone.com/.../...rGuideContent.jsp