You might need a new u joint.
replace it
3500.00
that depends on the motor that it has.
above the oil filter ,to the left.
below top end of radiator hose.
above oil filter.
maybe ablown head gasket
in front of the right rear wheel attached to the frame
that would be the throttle sensor.
Go to Autozone and get a haynes repair manual,it will show and tell you how.
That info is on pages 18 and 19 of the EF(Engine fuel) & EC(Emission control)section of the 1987 Nissan Truck/Pathfinder service manual.
probably 4 quarts. Any auto shop will tell you