how i look at it, if a car does 10k per year on average then 138 is a bit above, but if it has good service history, runs ok (no smoke!), all fluids are where there supposed to be (not dripping or leaking) then engine wise that mileage isn't anything to worry about. What i would do is give it a dam good test drive to include
full lock steering (listen and feel for any knocking, whining or grating) acceleration and breaking hard (look out for pulling to left or right) make sure that the 4h and 4low work correctly, while you are out try looking at the sockets i told you about to see if it solves the abs problem

if it does then make sure you put the fault back

look in the air filter box for signs of oil/soot, look at the vac pipes to see if they have been replaced at any time, test all the electrics especially the rear wiper!! another good indicator for how the mileage has been put on is stone chips and steering wheel wear (lots of chips and not much wear to s/w normally indicates motorway mileage!). How many owners has it had? this is also a good indication on its reliability
Some of the things i have said sound obvious but most people forget about these things when looking at a new motor, i myself have done it and bought a pile of c?&p before because it was shiny and looked good

especially if you buy off a dealer!! they are good at hiding faults with spit and polish
Hope this helps
Cheers Tony