Land Rover Repair: PO171 lean bank1 PO174 lean bank2, mobil delvac, maf sensor

Question
Hello John,
My "Service Engine Soon" light has been on for a couple of weeks.  I took it to a shop and the tech gave me these codes.  What do they mean and how can I solve the issue?  He said it could be a plug or a MAF sensor?  I looked up the part online and the price goes from really exp. to fairly inexp.  The truck runs great eventhough it has 108k miles on it.  
What type oil fluid you recommend for that type mileage?
The odometer digital backlight recently burned out.  Can see the mileage during the day but can't read at night.  Any quick fixes for that?  Thanks in adv. for answering all my little questions.

Answer
If I were to take a guess, it wouldbe a MAF sensor.  You have to decide if you want to throw parts at it and hope the guesses work, or see properly qualified service help.

It's tough to find truly qualified repair shops and technicians for these European cars.  Many people want to avoid dealers, yet a large number of the independent shops just don't have the necessary skills to go beyond basic maintenance

As to oil . . . we would use Mobil 1 5-40 SUV.  Alternates are Shell synthetic Rotella, or Mobil Delvac  5-40

The backlight is an hour's job, requires pulling out the instrument cluster.