Khyber has pretty decent torque and power for hilly area's. A well tuned car can take you anywhere you want if you are a bit skilled driver.
There is a Khyber in our family since 1998 we are the first owners of car and the car is in my use nowadays. Recently got it's engine overhauled for the first time. The fuel average i am getting is around 12kmpl in city with AC and around 16-17kmpl on highway with AC. But that depends on lot of factors and how the car is maintained.
Try to negotiate as much as you can for getting a good deal.
For body check the front wiper bay for rust issue's and the lower control arm mounting point's for rust damage. If they are too much rusty leave that car. They can't be repaired properly in Pakistan atleast.
Search for a thread Khyber - Performance after Complete Engine Overhaul..
A fellow Pakwheeler and I have shared our experience after overhaul there and some other discussion about the car.