The sensor is next to the thermostat housing and very close to the intake
manifold such that it's hard to get to with an ordinary wrench. The sensor's
hex is no ordinary size---it is 25mm. A one-inch wrench is too big, and will
round the hex---I first tried a one-inch crowfoot flare, which did not work.

A deep socket worked for me. It will need internal clearance of about 1 1/4 inch
to clear the plastic top (which protects the contacts) of the sensor.
Socket should not be too tall. Mine is about 2 3/4 inches tall and barely
cleared a nearby metal fuel injection line.

When using a deep socket take care that it does not tip against the plastic
top of the sensor. This top is fragile and can be broken by an incautiously
used socket. If that happens you'll need another sensor.

It is not necessary to drain coolant (as some shop manuals advise) as long
as the system is pressure tight. Leave the radiator cap tight and remove
the sensor. I lost a few teaspoons of coolant.

Replacing the sensor on my '93 gave me a less-rough idle.