I have a 2007 chevy silverado and need to replace the oil pressure sending unit.

If you have a 4.3 or 5.7 Litre engine (Silverado Classic Body Style), it is mounted on the back of the intake manifold in a brass fitting just under where the fuel lines come up from the transmission bell housing. If you have a 4.8, 5.3 or 6.0 Litre engine (Silverado New Body Style), it is under the left rear corner of the intake manifold and you have to remove the intake manifold to replace it.