$3500 isn't unreasonable. The real issue is the "unknown" - the CEL could be something super-simple, or it could be a $2k repair.
The low miles are a plus in some ways, but she'll need a thorough going-through, as the VH41 engines need to be run at higher RPMs (and go through a full cold - operating temp - cold cycle) in order to prevent sludge and deposits in the intake, the IACV, PCV, EGR, etc.
As BadQ said, the new owner can plan on $1500-$2000 (if they're a DIY type) in rehab (hoses, fluids, seals, injector cleaning, tires, etc). All the things that go bad from sitting idly OR short trips.
I'd definitely purchase it as a backup car.