That sucks dude, I know exactly what you mean. I run into the same crap all the time with Duramax parts, everything is ship direct and none of it is stocked at the PDC's:doh: Which means usually at least a weeks wait for me:mad:
Most likely its the pipe that runsfrom the back side of the water pump to the oil cooler. There is an o ring that has a tendency to leak. It could also be running along there coming from the water pump itself. Thats the most common leak that I've see on those trucks.
Tough break vinny.
Have you checked the return line where it comes out of the head on the drivers side, that banjo seal has a tendency to move when taking the line on and off.
You could have a few different problems going on. Usually the fuel guage issue is caused by the level sensor in the tank. and the low oil pressure could mean several diff things such as; fuel in the oil, bad pressure sensor, worn bearings, or something like that. Keep in mind that it's...