92 Jimmy digital dash problem

I have a 92 Jimmy with a 4.3 Liter v-6 vortec engine. I have a digital dash and I've noticed that my oil gauge is reading a full 80 psi...normally, it's never gone over 40. it will remain that way for a while then will drop down to 40. occasionally, i've seen it fluctuate between the two numbers. i noticed the car doing that about 3 days ago. my question is.....is this an indication that my computer may be going bad and giving me a false gauge reading? if so, how much would that run me? someone told me that it would cost me thousands of dollars and almost nothing in terms of trade in value because a bad computer chip would not give a true mileage. any truth to that???

You need to replace the oil sensor sender, at the back of the engine, beside the distributor. That will fix it. Noting is wrong with your computer.

is that something i can pick up at a parts store, or do i need to get it from a dealership?

Parts store will have it.