As far as the maintenance, since the QX4 was female owned, I doubt it has had anything done besides oil changes. I would ask your sister what she's done and when. Timing belt interval on our engine is 110,000 miles so you're probably there right now. It is around a $500 job with everything, including water pump, all belts, all hoses, thermostat, tensioners, and probably camshaft seals. I highly doubt your sister has done that... The timing belt usually lasts MUCH longer than the recommended interval but it is good insurance. I would also change: Front and rear differential fluids transfer case fluid (use ATF in this)
coolant
spark plugs (the two tools for plugs 1-5 and then #6 is under your rear seat) in-cabin air filter (behind glove box, this one will be nasty at 130k miles, should be $30 at a nissan dealership, $60 at Infiniti, but they are the same damn part #, I can get the part # for you on Monday if you like )
Let us know if you need anything There is a lot of info here - FAQ's
http://www.4x4parts.com/ubbthr...21482 and here - Nissan part #'s and maintenance schedule
http://www.4x4parts.com/ubbthr...10947