Sorry if this has been answered already,the search function isn't working

Someone @ work is asking me to install some electronic gauges for his 2001 Maxima,told him to give me a few days to research before I decide to do the job. The gauges are oil pressure,A/F ratio,and voltage. I've done gauges and stuff on other cars,but this will be my first Nissan gauge install.

Oil Pressure
I'm sure the oil pressure port is 1/8" BSP like most other vehicles;and the factory oil pressure "idiot light" switch is right by the oil filter,near the passenger-side axle. Correct?
Due to the size and weight of his gauge's sender,I'm going to run a hose off the tee fitting then mount the sender somewhere in the engine bay (fabbing a mounting bracket). I've seen Autometer pressure senders break off tee fittings before,and besides the sender would be hitting the axle even if I did mount it directly off the tee.

Air/Fuel
I believe I saw three wires coming from the front exhaust manifold's sensor. Anyone know what color the signal wire is? If not I'll just probe with a voltmeter.

General wiring
Is there a firewall grommet I can easily access to run the wiring into? Or where do y'all usually run wires through?
Is the factory gauge cluster dimmer controlled from the ground or positive side of the circuit?

Thanks for any answers. I'll try to take pics of the install if I do this install for him.

 

Oilpressure, once you run the hose make sure its tight on the barb because the pressure definetely is in the 50s.

AirFuel. Id just tap pin 61 or 62 from the ECU. White in color. They are the wires for the two front O2 sensors.

The gromet is actually on the drivers side behind the wheel well lining in the wheel. So you have to remove the wheel, then remove the entire wheel well plastic lining. You will see the large gromet where the wires go through for the Maxima.

Dixit