Nissan Repair: repairs, oxygen sensor, air induction

Question
So I went to Autozone, which does the 'check engine soon' codes sensor for free and this is what I got.(98 maxima w/manual transmission)

PO325, PO302, PO139, PO138.

I then got a diagnostic done at a local shop, and this is what they recommend.

Tune Up Package- 99.90
air induction cleaning- 89.90
fuel injection cleaning- 59.90
ignition coil- 141.30
O2 sensor bank 1 sensor 2- 288.21

plus labor it'll be around 800 dollars.

Does this all look right to you?  Also, the guy mentioned that he wouldn't mind if I bought the parts myself and let them do the labor and I wonder if that will be cheaper.

thanks,
Mike


Answer
Mike,

Replace the knock sensor that is code 0325
Replace the coils as this is a misfire condition
Replace the downstream oxygen sensor
Check the harness to the downstream oxygen sensor as it might be damaged.  It could be just the oxygen sensor is defective.  I would do it myself as it is easy except fo the knock sensor.