Oil Pressure Gauge maxed out

I have a 1997 Chevy Corvette, with the LS1 V8, 5.66L, 345hp engine. It has 117,000 miles on it and has been well maintained. Two days ago, after going through an automatic carwash, I noticed that the Oil Pressure is reading max on the gauge, 80PSI, and on the DIC, it is showing 128 to 130PSI steady. Also, recently I have run the battery dead due to leaving an aftermarket Satellite radio on accidently, that required a jump start. The car runs just fine, I've opened the oil filler cap, no oil spewed forth, no hissing, so I'm thinking its a bad sensor. My questions are these:

1. Is it okay to run the motor like this, assuming the idication is false?
2. What is involved to replace the sensor and/or gauge?
3. If replacement is needed, what have you seen as a ballpark cost with parts and labor to do the R&R?
4. Which is more likely the culprit, the carwash or the jumpstarts?

Thanks much,

John