Under the hood, on the passenger-side of the firewall, down low & just above the catalytic converter.
Yes
in the glove box
R-134a
if your 2001 path has in-cabin filter (mine does not) they (two) will be located behind the glovebox. you will need to remove glovebox and back cover to expose the filters.
YES
does not have one as far as i know
On the each wheel adjacent to the brake caliper
if you mean highest setting being the fan speed, then the problem is most likely the fan speed resistor located in the blower motor box area
low pressure side is located closest to the front of the vehicle on the right side as you are facing the engine it shoulh have a screw on cap with the letter L for low pressure.
no they are to big
The 1995 Nissan Pathfinder headlight relay switch is located on the firewall in the engine compartment. The headlamp relay switch will be on the drivers side of the firewall.
you can purchase a repair manual for your vehicle from most auto parts stores, or try autozone.com and look under component location or repairs for the Nissan Pathfinder.