CEL light has been intermittent for a couple of months, but now is steady and "permanent." My code reader indicates it is Bank 1 Position1 (upstream sensor on passenger side)

The typical reaction is to replace the sensor and clear the fault. However, as I studied the issue, it became apparent that there are situations that a sensor fault is a symptom of a larger problem. (fuel injector, valve cover gaskets, shorted wires) My concern is that if I replace the sensor I will be masking a larger problem.

My local independent shop will charge a $175 for a diagnosis. And if it is a bad sensor, an additional charge of about $300 to replace. Their shop rates are $165/hour.

I'm creating this thread to create a written record for others to refer to for guidance on this issue. i.e., what was cause of failure, how was it repaired, what did it cost

So my question for anyone that has dealt with this or for tech/mechanics is this: If you had this code, did a repair involve any additional repair or was it simply a failed sensor.

Additionally, I will follow up to conclusion on my findings and solutions.