Oil light on dash lit up but I have no headlights or power to anything

Let's do two things. First let's check for codes.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Next we need to go back over the repair and look for connectors even if you have to take them apart and reconnect them.

Lastly we need to check the oil pressure with a gauge just to be sure it is an electrical issue and not an actual oil pressure issue.

https://www.2carpros.com/articles/high-or-low-engine-oil-pressure

Let's start with this and go from there.