Nissan Repair: EGR system failure & knock sensor problem, nissan maxima, knock sensor

Question
Hi, I have a 1997 Nissan Maxima with 131,000 miles. To date I haven't had any issue with this vehicle at all. I do 99% highway driving and the car is garaged. With that said, recently my check engine light came on. I had the codes pulled and it was determined that I have an EGR system problem and a knock sensor issue. Also, over the last couple of months I have been hearing a weird engine sound everytime I cold start my vehicle. It basically only happens in the morning and then it goes away. Well lately I've been hearing it when I start the car in the afternoon as well. I asked the guys at work and they seem to think that it's the starter that's going but I'm not sure. So my questions are: How important are these system failures and ~ what should I expect to pay to replace or repair them and lastly does it sound like it's my starter if so how much does it usually cost to reapir that. Any information that you could provide would be greatly appreciated. Thank you.

Answer
The cost of a rebuilt starter is about $120 plus installation.  If you are handy I would go for doing it myself and save over $100 in labor.  The cost of the EGR and Knock sensor will be over $100 each plus labor.  If the starter still works but makes noise in the morning I would suggest taking it apart and lubricating the planetary gear set and reinstalling it.