96 villager knock sensor 1 fault code

Recently, my wife was driving the above van and it stalled on her at a red light. Moments later, she was able to restart it.
I had Autozone check for code, it says "Knock Sensor 1 Fault", I think the code was P0135.

What's this due to? AND, should I replace it? Or is this bad gas causing problem?

Autozone sells a new knock sensor for about $175. Is that the only item that requires replacement, or is it a major job to get to it?

Thanks.

P.S. The van has 99000 miles, but I'd like to keep it for 1-2 more years, so some reasonable expenses would be OK.

LEAVE THAT THING ALONE. It only has one purpose and that is to tell you that something else is wrong with your van. Get a tune etc done. You may have many other symptons that caused that code. I would ask her if she used a diffrent grade of gas that can sometimes trigger that code. It is there to sense vvibrations and detonation I think is the term. Do not replace it the part is 175 the labor is 5 time that.

I would definitely agree with IH8SPM . You probably did have something rattle around in the engine when it stalled. Maybe a miss or something cause it to vibrate the motor then stall. Triggering the sensor. Tune -up & oil change time.