I have a 1999 Chevy Lumina 3.1 ltr with 327000

The coolant sensor temperature is usually found just beneath the cylinder head, on the engine block.

You just disconnect the 1-2 wires and then undo it with a wrench.
The sensor will look like one of these:
1999 Chevy Lumina ltz 3 8 v6 coolant temperature sensor Google Search

Just be aware .. you may have TWO such sensors on your vehicle.

One sensor (usually with 3-4 electrical pins) is near the thermostat and works in conjunction with other sensors to regulate fuel/air according to engine temperature.

The other type of sensor is in the block near the cylinder head. It sends a signal to the temperature gauge on your dashboard ONLY. If your temp gauge constantly reads too hot or too cold .. this one is the culprit.
If it's a running fault .. speed .. rough running .. fuel. It may look like this:

Could be two different issues.
The low coolant light could be low coolant or a faulty switch.
The other problem could be a long list of things including a fuel pump, a relay, the ignition module, or other things.
You would need to figure out if it is lacking spark or fuel to know which system to test.

Is the radiator full? make sure there are no air pockets in the engine block. Check the coolant level often.

There is an idler pulley and tensioner on the serpentine belt. They can cause this noise.

Yes, pull off cap when radiator is cool and check fluid. If it is full you may just have a bad sensor in the radiator.

You need to repair the low coolant condition before any more diagnosis. If the coolant in the radiator is low that's what the light is telling you. You may have a coolant leak. fix that first then make sure the cooling system is full. Use coolant (50/50) not water.

The fact that the oil was low would not be from the oil pump, but from wear in the engine. If it is not smoking when you start it or as you drive, you can probably keep it running by just keeping the oil level checked at each fuel fill-up. As for the car shutting off, you didn't say if the engine seized or got real hot. A low oil pressure problem should have triggered a warning light before the problem got to the point where you lost the engine.

If the car ran after you added the oil, you got lucky and need to always check it.

When filling the coolant system you need to have the car running with radiator cap off and you can also burp the coolant hose while filling the system to remove any air. The system may be full for a while until thermostat opens and sucks the coolant out of radiator which is the perfect time to add more to top it off.

Disconnecting your negative battery cable for 10 minutes will reset the computer and shut off the light.

this is a common problem with gm vehicles your low coolant sensor is bad, depending on which engine you have,it will be located in the coolant jug, or it will be a 2" square sensor near the top of the passenger side of the radiator end tank

no fan comes on when engine cold start up .but it will come on when you turn on air conditioning or defrost on .if engine idling a while when temp get 190 degree the fan will kick on.if over heating you got air in system .wait until cools check coolant add more .crank engine let it idle few. minutes when start warming up turn off engine wait a while before removing radiator cap so you wont get scald.add more coolant .crank it again starting warming up turn off engine wait a while .add coolant .keep doing this procedure until your coolant stop dropping off .if you do this more than 6 times you got a leak some where.check crank level for signs.if oil level higher than normal.if everything looking good.when engine cool make sure add coolant to over flow jug cold level mark.