I have a 1978 280Z all stock the oil pressure gauge has suddenly stopped working, that or i simply have no oil pressure. I do know that there was an oil leak around the sending unit, someone decided to screw the sending unit still wired up further towards the block and now it reads nothing. Is it as simple as unscrewing the sending unit away from the block and it will start reading the pressure again, or am i gonna be getting a hold of that person to buy me a new unit?

I assume the tightening was done at the fitting that goes into the block, not the body of the sender. Screwing it in further should not have been a problem, unless the wire was twisted until it broke. Check the connection.

It was the sender itself.