Ford: Error Code p0125, coolant level, oxygen sensors

Question
Sir,
I have a 2000 F150 4.6 V8 2WD.  My service engine soon light recently came on, so I had autozone run the code, and it throws the p0125 code.  My coolant level is fine, and I haven't checked the thermostat, yet, but my question is, if the problem lies with the ECT sensor and not the thermostat, first, do I have an ECT sensor, and if so, where is this located?  Also, can this Insufficient Coolant Temperature problem be causing my truck to drive rough?  Occasionally, when I give the truck just a little bit of gas, it seems as if the vehicle will stall out.  Thank you for your time.

Answer
While this code can affect driveability, it typically doesnt

When was last tune-up done, and have the oxygen sensors been tested?

do you add a good fuel system cleaner 2 times a year?

The P0125 code usually indicates a slow thermostat.

If you have not replaced it in 10 years... it is very overdue.