None of those codes are anything to be worried about....really.
P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem: http://www.obd-codes.com/p0121
P0171 - System Too Lean (Bank 1): http://www.obd-codes.com/p0171
P0174 - System Too Lean (Bank 2): http://www.obd-codes.com/p0174
P0303 - Cylinder 3 Misfire Detected: http://www.obd-codes.com/p0303
All of that could be caused by a bad Throttle Position Sensor. They aren't terribly expensive (quick internet search shows $40 to $150 depending on which one our engine uses) and it's fairly easy to get to to change out.
The high pitched whine may be totally unrelated to the above problems and just happened to show up when everything else went on the fritz. Hard to diagnose the location of the sound with the description you gave. Can you upload a video?
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