Nissan Repair: Infinity QX4 knock sensor, horrible pic, sensor replacement

Question
Dinger
My 1999 QX4 has just been diagnost with a knock sensor replacement code. I know the dealer is going to rip me a new one on labor cost. Where in the engine compartment is the knock sensor located on my truck and do you recommend replacing it myself?  

Answer
Hi Steve,

I have a crappy picture of it. If you supply me with your email, I will gladly share it with you. It's located at the middle, top towards the rear of the engine. I looks like it's the last sensor in the middle towards the rear of the engine. From this horrible pic, it looks like it could be on the square side as opposed to round.