What does a oil sending unit look like?Where is it ?

The oil pressure sensor is in the engine block right in front of the oil filter. It's a little canister with an electrical connector on it. It's easy and cheap to replace the sending unit. The oil pump should have a screen on it.

its about 1/2 inch tall and about 3/4 inch wide and round most of the time located on the side of the engin that is closest to the oil pump