Chevrolet Repair: Instrument cluster, oil pressure guage, oil pressure gauge

Question
I have a 2003 Tahoe the oil pressure guage is on 80 psi when truck is running is the oil presure sensor bad or is the cluster defective? The truck has 28000 miles, I took it to dealer cause the 4 wheel service light came on and they told me it may be a bad computer cause of all the other codes that they found but they where not sure at $600 to repair they better be sure. Is there any way to check if its the computer or the cluster as far as the oil pressure gauge is concerned? I removed the plug on the sensor and the guage stays at 0 psi when truck is running. I understand that the tahoes had bad cluster motors is that a possibility? Sorry for all the long question.Thanks for your help any input will be appriciated.

Answer
thats a tough one. tell you what, take it back to the dealership and let them do the work. if it doesnt fix it with the computer, tell them you wont pay for it. at that point, they will put the old one back in and replace the dash. but ill tell you what. it does sound like either the sensor or the computer if you took the plug off the sensor and the guage went to 0. maybe you should replace the sensor first. couldnt cost too much to do that.