"low oil pressure" warning

Could be. Low oil pressure is caused by two things mainly. Your oil pump is designed to supply a certain pressure to your motor, they have a pressure regulator built-in. 1.) The pump or regulator can fail causing low oil pressure. 2.) A component or multiple components in the motor can fail causing an increase in oil flow to that area which causes a pressure drop or low flow to other areas of the motor. Most bearings in your motor are metal on metal and use a small layer of oil in between to operate. If the oil cannot get to the specific bearing the metal on metal contact will destroy the part. If any of the bearings in the engine were starved of oil for to long they will be damaged. How hard was it to start the last time it ran. A reman motor is not your only choice but it is the least risky. You could also get a used motor, some salvage/wreckers will show the used engine running and may install it with a limited warranty. Or if you can live without your truck for a week or two your motor could be re-built, but if the bearings went they may have damaged other components.

I'm sure the mechanic is knowlegable enough to know the difference between a faulty sending unit and a toast motor. But you never know.

I have a 2000 Chevy Suburban with a 5.3 Vortec motor I had the same problem and had to get my motor replaced , I broke down the old motor and saw that my push rods were bad I need a pliers to pull them out I had a build up so if your car is still running you need to go in and get it rebuilt or you're going to have to get a new motor real soon

Your oil pan bolts are loose, had the same thing happened to mine would drive it for 15 minutes, low pressure light would come on and I would have to pull over and we stopped vehicle and restart vehicle and then fine for 15 minutes.found loose oil, pan gaskets, bolts tighten the bolts problem solved

I think its as the gentle men saying because I broke one of the bolts when I was tiding the oil pan by the air gun so it might be loosing oil from the oil pan and because I checked the oil yesterday and it was at low level I changed the oil today but I am going to put another new bolt tomorrow and change the oil another time and the gasket