Hey all!

It looks like i'm starting to have some engine problems on my 96 Maxima GXE. Yesterday i started the car and after driving for a few minutes the "Check Engine" light came on and i was like wtf?? Anyways took it in to my local dealer and they told me that i need to get a couple of sensors replaced. The 2 sensors i need are the Oxygen (O2) Sensor and a Knock-off Sensor. The service guy said that the O2 sensor is like $400 bucks and the Knock off sensor is $625 bucks?? My question is where can i find these parts that fairly cheap?? Any suggestions would be greatly apprecitated.

Thanks all!