Please help ASAP. Gauge reads NO oil pressure

I was intalling some aftermarket oil gauges(pressure and temp) and I am using a spacer between the oil and cooler(2002 SVT) I had installed everything but the oil filter and went to get some dinner. My liitle brother ( Love him to death but wanna kill him sometimes) started the car. I heard it and ran out and shut it off right away. It ran maybe 4 seconds 5 seconds. Clean up the huge mess and throw the filter on it and fill her up with some mobil 1 and my aftermarket guage reads around 65 pounds of pressure but it jumps around and when I hit the throttle it dips a bit before the pressure rises. But the factory gauge reads zero oil pressure. But there is no idiot light for no oil pressure lit up?? What do you guys think I should do?? Trust the new gauge and drive it to work tomorow?? hitch a ride and look it over tomorow?? Its to dark but I dont see a ton of oil in the valve cover. I took the filter back off and its full of oil so oil is moving through the engine. No noises whatsoever. No leaks at all. I cleaned up the mess and there are no leaks. So I should have oil pressure right?? why did the factory gauge suddenly die when it ran with no filter?? Anyone know where the stock sender is??