Crankshaft position sensor

[nkostop]

So I recently got an engine code on my 99 yukon after doing an oil (just a coincidence I hope) and it was for the crankshaft positing sensor. There is a terrible knocking sound that happened right after I got my truck from the oil change being done. I'm pretty sure my crankshaft pulley is bad because I've had trouble with it before. I'm thinking that the pulley screwed up the sensor and the valve timing is way off. Any other opinions? Can I still drive the truck with bad valve timing? Lastly, is it an expensive job because I don't think I could replace the sensor myself. Thanks, any feedback is appreciated

 

[nkostop]

Bump

 

[2door2wheel]

the sensor is not that hard to replace its on the bottom of the timing cover Its right behind the crank pulley on the passenger side of the engine. You will see the wire connector going to it.