2008 Ford Expedition 5.4L P0012 Fault: Did a Computer Reset Really Fix It?

I recently drove my 2008 Ford Expedition with a 5.4L engine (56,000 miles) approximately 100 miles out of town for a high school reunion. During the trip, it ran fine, but when I arrived at my motel parking lot, the vehicle would barely idle. This was the first time I experienced this issue—previously, it had run smoothly during all stops on the road. After checking into my room, I restarted the engine, and it still idled roughly with the check engine light illuminating. A fellow graduate who lives nearby performed a diagnostic and found code P0012. After researching online, he concluded this is a complex issue beyond his comfort level. Two days later, the vehicle was towed back to a local mechanic, who only performed a computer reset (not just clearing the code), and the idle improved significantly. I drove it home the next day, making one stop for gas—no rough idling or check engine light issues. My question: could this simple reset have truly resolved the underlying problem? As a 63-year-old female, I'm hesitant to drive this vehicle again without confidence in its reliability. Should I take it to my Ford dealer or a trusted neighborhood mechanic instead? While restarting a laptop often resolves minor glitches, is it really that straightforward for a vehicle that previously wouldn't idle properly enough to reach a repair shop? Any insights or expert opinions would be greatly appreciated.