I've never had to change one but most people I know who did said they had moisture down and around the sensor. They said it wasn't a bad job as the intake manifold is a dry manifold so you don't have to drain any coolant. You'll need a fuel line disconnect tool and basic hand tools. They said the sensor has a plug thats a pain in the butt to unplug, they use two small pocket screwdrivers. As mentioned they took some heat resitant silicone and made a "wall" of silcone around the new sensors so water can't run under the manifold and into where the sensor is located.