My Volvo S40 1.9T 2002 has check engine light on for almost 2 yrs. Checked the OBD codes and got three codes:
P0237
P0171
P0131
I was told by my mechanic (a mobile mechanic, not a Volvo specialist) that the car needs a new Turbo charger.

My questions:
a) Is the diagnosis correct?
b) If so, as it's an old car, can I try to get a Turbo charger from the junk yard, used from eBay, or should I only buy new?
c) If new after market OK or should I buy OEM?
d) What should be the typical labor charge for installing the Turbo charger be?

Thanks, greatly appreciate your feedback!