Job for a pro. Inlet manifold has to come off to allow access. Thermostat is located down the side of the enging, beside the water pump. Get them to check timing belt, water pump, belt tensioner...
I tried to add this under discussion but it doesn't look like it posted..
Did you make sure you checked the Front Bumper Reinforcement, also? Explains how to do it here:...
(1993 Pathfinder XE) First start by taking the front bumper ends off (3 nuts on each). Then remove the entire fog light assembly including the plastic trim surrounding it. Then there will be 4 nuts...