In a message dated 96-07-24 14:44:06 EDT, you write:

>1)If I use heat to get it out, will it damage the sensor?

Doubtful.  This device "lives" in pretty hot conditions.  Mine have all come
out with only moderate wrenching.  Try some liquid wrence if you haven't
already.  If you apply heat I'd do it by applying heat to the exhaust pipe
and let the heat work into the sensor from the threaded end.  I suspect it
would be damaged if you just "torched-away" at the body of the sensor.

>2)Should I replace the sensor anyway since it's probably original?

The service schedule calls for it to have been replace by now, but that
doesn't tell you if it's still functioning o.k.  I don't have the procedure
handy, but a while back someone sent a O2 sensor diagnostics procedure to the
list.  You could find it in the archives.  Nix that.  I found it.  From Roger
Bowman:
Oxygen sensors can be tested, using a scope or even a 
good high impedence voltmeter.  The sensor itself "puts out" from 0 to 
1.1volt signal when sufficiently warm; the computer looks for "cross-overs", 
or the number of times a signal crosses through the .45v point.  A healthy 
ox sensor will not spend any time at .45 volts.  Since this voltage will 
change directly with the amount of oxygen in the exhaust, the sensor implies 
the mixture, the computer is then able to make corrections in the dwell time 
of the injectors, or whatever to make the mixture come out just so.

Determine the output (sensed) wire; the other two are heater leads to get 
the sensor on-line more quickly.  Warm the engine, and watch for voltages 
above and below .45v, and rapid changes.  This would indicate a good sensor. 
 If the voltage parks at a high (.7v) or low (.2v) level, try richening or 
leaning the mixture and watching for a change.

low volts = lean: 
high volts = rich.

Testing the sensor on the workbench is also possible using a propane torch 
to warm the sensor and keeping track of the recovery time once the flame is 
removed.  The sensor should appear to be an "open" circuit when cool when 
tested for resistance.

I got this from a posting by Rick Kirchoff via Cary McAlister, from the 
Z-Car mailing list.   

>3)Is it nec. to have a working sensor for the engine to run well?

Yes.  If the engine is (was) running fine, the O@ sensor is likely o.k. also.

>4)Is it nec. to have a working sensor to pass emissions tests?

Probably.

>5)Finally, since I've had my '87 (few weeks), I've noticed that only the 
>large plug coming out of the O2 sensor is connected....the little plug 
>was just hanging loose.  Someone told me that this means that the O2 
>sensor wasn't really hooked up anyway.

1(or 2,  2 I think) wires are for the sensor's heater and 1(or 2,  1 I think)
are for the actual sensor output.  If the heater is not connected, the
sensor's output won't be reliable until the exhaust warms it up sufficiently.
 If the sensor wire(s) are not connected, then the control unit never sees
the oxygen sensor input and the engine may run bad, waste gas, polute too
much, or all three.