2004 pontiac grand prix throttle position sensor

I took my car to pep boys and they told me the throttle position sensor and the accelerator pedal needs to be replaced. Though I just replaced the pedal a few weeks ago. Auto zone told me that the throttle position sensor cant be replaced, it has to be the entire throttle assembly. Yet they sell the position sensor online that is an exact fit for my car. Advance auto parts sells the exact fit for my car as well. So how do I know if I need to replace the entire assembly or just the sensor. Especially since the sensor cost roughly $350 and the pedal sensor was about $55.00. Pep boys was goona replace both for 500. and the sensor part that they quoted me for was only $150. Help someone, anyone.

I can attach photos of engine if clarity is needed.

lets go back a little, what codes did you have and what kind of problems are you having with your vehicle? If you replaced the sensors on the gas pedal then you don't have a throttle cable, right? So, are the codes you have from your vehicle, is it for a TPS or is it for a throttle actuator control (TAC)?