this may help some
father has a 95 SE with the electric speedo
a few times spread out he had the speedo die and the idle go bad, car is a 5spd so no shifting issues
the last time it happened I started searching and I had determined that it should be a bad VSS. but this was not the case
my father noticed that it seemed to happen when the engine was under alot or torque
turns out the plug for the VSS id pulled tight and orientated in a direction were it will hold water, just like the parking brake cables....

anyway, he sprayed some silicone of the sensor to keep it working and cut the tie wrap on the sensor so that the wires wouldn't pull on it anymore and it was orienteted in a direction to not hold water if any got in there
hope that helps, also the VSS is a hall type sensor, it shouldn't ever wear out, it is just a spinning cylinder inside another that creates a voltage difference as it spins