Oil pump on 05 gmc 1500

it is in the center of the back of the oil pan...might have to take the skip plate off to get to it.

The oil plug will be located on your oil pan. If you checked ther are you sure you checked all areas? I have never seen one anywhere else. Especially on an american made vehicle. I don't know your experience level but the oil pan is located just in front of the transmission under the engine. I hope that helps you find it.

have it tested using a manual gage if still low then main baring ore most likely bad that would mean a over hall if is really low and bearings bad should be making rattle noise when started up first few seconds

I doubt it....It could be a totally worn out engine.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

if it shows low oil level its possible bad "level sensor "located on oil pan.if it shows low oil pressure possible oil "pressure sensor"

Information courtesy of synthetic-direct.ca
Chevrolet Suburban/GMC Yukon XL, 2000-05 Chevrolet GMC Trucks Silverado, Sierra, 1999-05 Chevrolet Venture 2000
Turn the ignition key to the RUN position. Fully push and release the accelerator pedal 3 times within 5 seconds. If the CHANGE OIL SOON light flashes 2 times, the system is reset. However if the light comes on and stays on for 5 seconds, the system did not reset. Repeat the procedure if the system does not reset.
Best of luck.
Greg

the knock sensors are located below the intake plenum,or,upper intake manifold as some call it, they screw into the lower intake, the front one is sensor 1, the rear is sensor 2. it is wise to change both if you have some miles.since you are going to be buying a gasket set to do this job.the sensors are cheaper than the gaskets.

Where i s oil drain plug?
GMC 2008 Sierra

if you went to a dealer then that sounds about right. they tend to be expensive. you got to remember though that most the time 90k mile maintenence includes radiator flush, oil change, tranny oil change, emissions checks, possibly water pump check. cooling system pressure check. abs checks, brake checks, steering and suspension checks. there is alot of maintenance that can be done. you need a list of the stuff they are trying to charge you. honestly if they do all the work required then 3300 my not be to bad