hey er' body

i am confused as to what the knock sensor and the oil pressure sender gauge are?
i called the dealership and they said that a new knock sensor what 199.99!

the only thing i have to go on is the fact that i recieved two sensor looking things back from my machinist that are broken and in the fsm, those are they only 2 sensor things that need to be installed before the timing chain and head go back on.

also what are the bolt measurments for the timing chain cover?

thanks