Quick highway miles should have left hardly any signs on that car.
I'm not much into car sales so I don't know the price relationship, but it sounds as though its 5k or more below what a lower mileage car would bring. I would have the car professionally checked out and if you wish to slowly put another 100-200k on a car getting such a vehicle could be economically advantageous.
Bosch Master, ASE Master, L1
33 years MB technician