Ask for maintenance records, if available. Look for engine oil/tranny fluid leaks. Look at the under carriage to see if it's getting leaked on or if it is clean. How clean is the engine bay? Allow for 'usage', but see that stuff is maintained. How are the tires especially the front ones? Are they worn unevenly. May speak to ball joint condition. Try everything, turn signals/hazards, wipers/window washer, radio, interior lights, exterior lights.
Just so ya know.....102K for a diesel is pretty much just getting broke in. A '99 with that mileage hasn't been driven too hard.