Fuel and coolant gauges don't work

Chev dashboard of this vintage are aweful for needing rebuilt. The tach quits and then the fuel guage and then the speedo......

You have a failed sender unit in your fuel tank

scrap it

Did you have the vehicle control modules checked for DTC'S - diagnostic trouble code's ? Not going to a part's store an having it checked . Need to have a professional type scan tool hooked up , check code's in the BCM - body control module , the instrument cluster can also have DTC'S stored . Auto part stores can not check these code's .Viewing engine sensor data to the PCM to see what the real temp. is . Coolant temp. sensor is an input to the PCM/ECM - engine computer , this info is sent to the instrument cluster over the class 2 serial data network .Do you know what a automotive communication network is ? Plus GM had stepper motor problems in their instrument cluster's from 2003 to 2006 . The stepper motor is what controlls that needle .
How to repair GM Instrument Cluster Speedometer Gauge Stepper

Sounds like a blower motor resistor. Not an expensive part, fairly easy for a mechanic to change. Located usually behind the glove box door.

The oil pressure gauge on my 2003 Avalanche reads "0" and activates low oil pressure warning. Oil level is OK and engine does not sound like one with with no oil pressure; AKA no knocks or ticking. The mileage is 50,000 on this vehicle any ideas as I with no gauge I am leary of driving it? Please advise!

Common problem on the 03-06 Avalanche instrument clusters, it's caused by failing stepper motors on the cluster's circuit board and it can be repaired. Check this page for more on how to get it fixed - Avalanche oil gauge fix

Oil pressure gauge is not getting good ground. Check wire.

the sensor is located at the back of the top of the engine, behind the distributor. Could be the sensor or the gauge itself. Probably the sensor stuck.

You have a problem with the stepper motor gauge that Chevy used in the 02-06? Avalanche. All the gauges use the same stepper motor. They just go wonky and do all kinds of weird things. I have replaced two on mine already and two more are now acting up. There is a guy selling the motors and the repair for this problem on E-bay.