It would be worth that much if its not rotted in "bad" places,it appears minor on the exterior...I paid a lot less for my 85 diesel Suburban K10,but its got some cancer here and there too..and needs tranny work..
I'd ask if they would take 900,if they say hell no,and its decent bodywise,and runs OK,you can always go up from there..most people price things higher than they'll actually take for it knowing the buyers will want to bargain..
The diesels are OK,no powerhouse,about the same as a 250 six ,good low end torque,low revving engine-- but they give better fuel mileage than a gasser,and wont stall like a carbed engine on off roading hill climbs..not for everyone,you get used to their quirks after awhile...they can be hard to start in frigid weather if the glow plugs aren't "right" and they have a few well known problems like the starter breaking the block if you dont use the front brace on it,and the harmonic balancers get blamed for making the cranks break,though many think its the cranks that were weak..and not every one has these issues..