Sanger Gauge Issue

I have a 2008 Sanger V215. After summarizing recently, ran it with the fake-a-lake a couple times. The second time the Oil Pressure gauge just stop working. Worked fine the first time, then flickered a couple times during reset on second turn of key, but eventually just sat at zero on later starts. The other gauges in the cluster work fine (temp., & fuel). Is this a gauge issue or oil pressure sender issue? Anyone else encounter this at all with these Medallion II gauges? Have an appointment with a mechanic, but really would like to do it myself to save money!