As already mentioned, allot of this depends on where you are getting it from, meaning are you able to inspect the truck yourself before buying it. If not, I would insist on a mechanic having a look for you. Post the location where you are buying the truck here on this board and ask for recommendation of a dependable mechanic in the area. Ask the seller to take the truck there and have it checked out. It should cost you about $100. At a minimum, you need to know if there are any codes for the engine or transmission and have the suspension inspected. Also, have all of the accessories checked out.
I have a 2002 with 140,000 on it and I would drive it just about anywhere. At this point, it is well maintained and I have a reasonable degree of confidence that there is nothing that is about to go. I don't see how you can determine a fair price without knowing what may need to be replaced in the short run.
These are some of the maintenance items that commonly need to be addressed, especially for vehicles over 100,000 miles.
Brakes $200-$250
Struts $400-$500 (all 4)
Tires $400-$500
Muffler $300-$350
Wheel Bearing $80 each
Upper Control Arm and Ball Joint $110
CV Joint $75
CV Joint and Axel $370
Tie Rod Ends $28-$40
This the cost for the parts (excepting the muffler and tires) presuming you can do the work yourself. Even if your timing belts and transmission are fine, the maintenance repairs add up quickly. You really need to find out about all of this before making a decision.
LMHmedchem