I have had the car for 5 years with minimal problems and it has 96K miles. It has had a slight knock that I have heard at times. I have had it tuned and it is super fast. But when I had the control arms being replaced at a shop that works solely on Land Rovers they said the noise is the timing chain and the plastic guides and I really need to get it replaced. They wanted $6,000 for that. That sounds really high. What is a normal charge for that? and do these need to be replaced?