I'm pretty smart on the oil pressure system and have still been fooled by the electrical gauge and associated system. There's a reason the FSM expects you to use a mechanical back up. Ideally the mechanical gauge is connected to the oil pressure sensor location via a hosed connection... to avoid errors due to engine vibration. That's probably not necessary if you're simply doing a go/no-go test. Be careful and stay safe while trying to read the gauge with the engine running!
None of your work should have affected the oil system. It's very likely you don't have an issue.