Hello and welcome to just answer.The problem will usually be a failed stepper motor in the gauge cluster.There are updated stepper motors for the gauges.Most speedo/tach repair shops can easily replace the stepper motors.Oil pressure sensor failure would be easily seen with a scan tool that reads engine data.If the engine data parameter reads normal then the stepper motor has failed.If the parameter reads zero then the sensor has failed but this would cause a warning message so I suspect the gauge stepper motor has failed.
Are stepper motors available at retail auto parts stores, or are they available on line?
Here's a good website to purchase the stepper motors.
Thanks. I will give it a try.