I recently got a Jaguar 2003 X-Type 3.0 with 79 K miles on it.

What is your question?

I had the care looked at and there's a knocking noise to it and even louder when revving up the engine. I was told it could most likely be the Piston rod.. My question is whether it can be fixed and if so roughly around how much? A mechanic I know says it can be fixed underneath without having to take out the engine from the top..