I've got a well-maintained '92 Accord sedan, with just 126,000 miles. Today, without warning, I was unable to shift from park without first using the shift reset slot. What's wrong?????? Is this going to cost me more than the car is worth????

 

did you forget to press the brake pedal? h:

 

The solonoid could be out on the shifter. It releases the stick when you press the brake pedal at which point you can move freely through all the gears except R and P.
That's if it's like the Civics set up, which I should think it would be pretty similar. And you can probably stick you key in a release hole to set it free. You can also use keys similar to the factory keys, and you'll have to have one handy if you decide to drive with the car in that condition.

Assuming that's actually what happened.