Replacement of speed sensor switch what is the cost of repair

Hello, did the parts store perform needed pin point testing to drill down to the source of a code that was set from the warning light? I'm certain the answer is "no", so therefore, replacing a part is maybe not a good idea until proper testing has been performed. What about wiring? Control modules? Tone rings? Parts stores are in the business of selling parts. They 'help' with code reading to sell parts. Seeking professional guidance from those experienced and skilled is of incredible value.