What is a fair price for a 1988 John Deere 850 with 1400 hours.

I ran across one for sale with FEL and Backhoe. The tractor looks a little rough. The hydraulic cylinders on the backhoe need to be replaced and the hydraulic lines look cracked and need to be replaced. There is a pool of hydraulic fuild below the backhoe. The owner was not present when I looked at the tractor so I did get to hear it run.

What is the cost to replace hydraulic lines?

What is the cost to rebuild the hydraulic cylinders?

Here is a link to some pictures of the tractor.