This is information for my 2008:

1 - Fuel Injector 2
2 - Turbocharger Vane Position Sensor
3 - Fuel Injector 4
4 - Fuel Rail Pressure (FRP) Sensor
5 - Fuel Injector 6
6 - Fuel Injector 8
7 - Glow Plug 8
8 - Glow Plug 6
9 - Engine Oil Pressure (EOP) Sensor
10 - Engine Oil Level Switch
11 - Glow Plug 4
12 - G106
13 - G102
14 - Glow Plug 2

 

Welcome to DieselPlace

Here is a video that will give you an idea.
( person doing the video does not hold camera well)..

 

Thanks guys so much. I found it. Now I am just trying to get the connector off. Can barely fit my hands in there and not feeling a latch or anything.

Do I have to remove the oil filter to get in there?

 

Remove the left wheelhouse inner panel. Refer to Wheelhouse Panel Replacement in Body Front End.
Important

Clean the area around the sensor. Do not allow debris to enter the engine.
Disconnect the oil pressure sensor electrical connector.
Only takes two finger to unlatch.

Using J 41712 , remove the oil pressure sensor (1).
Installation Procedure

Notice

Refer to Fastener Notice in Cautions and Notices.

Apply sealant GM P/N 12346004 (Canadian P/N 10953480), or equivalent to the threads of the oil pressure sensor.
Using J 41712 , install the oil pressure sensor (1).TightenTighten the sensor to 30 N·m (22 lb ft).

Connect the oil pressure sensor electrical connector.
Install the left wheelhouse inner panel. Refer to Wheelhouse Panel Replacement in Body Front End.
Check and add engine oil if necessary.

This might help you how to disconnect connector.
https://www.silveradosierra.com/vortec-5-3l-v8/oil-pressure-sensor-electrical-connector-t21908.html

GM Part :98027456 SENSOR, Engine Oil Pressure/Temperature, SENSOR,ENGINE OIL PRESSURE(ALSO ORDER GASKET 94034148) $79.02

Production date on the door is 12/4; it was sold to me as a 2005. At the gauge cluster it is reading high when it gets warm.

Most likely you have an LLY motor

I would verify and put a machanical gauge on befor anything.

 

If that doesn't fix your issue then it could be the cluster. 01-07 OBS have known clusters issues. In this case I think it is the OPSU