I have a 2000 chevrolet venture and the low oil pressure light is on is this the oil pump or could this be the oil sending unit

I WOULD CHECK OIL PRESSURE FIRST, IF OIL PRESSURE OKAY,OIL PRESSURE SENDING UNIT FAULTY MORE LIKELY.IF OIL IS LOW YOU WILL HEAR RODS KNOCKING NOISE.

{: ) It's either of the two or it could be both. With or without the oil indicator lights on, you should check your oil on a regular basis before any trip. It's very important. In this case, the first thing you should do is to check for proper oil level. If it's below the mark, add oil and then inspect for any sign of oil leaks on your engine.
Your vehicle has an oil level indicator and an oil pressure indicator. If the engine is running low in oil, the oil pressure may drop as well, If the oil level or the oil pressure drops below safe limits, the indicators will turn on and a trouble code will be stored on the PCM.
If oil level is ok and you found no leak, but the indicators still on, that's the time you need to have it serviced. It should undergo oil pressure test, scan for codes, and check the wirings. Sometimes a loose terminal connection at the oil sensor switches can cause it, A scan tool can tell if the readings on your cluster are consistent, otherwise your gauges or indicator circuits may also be in question.
I just hope we don't have a loose compression problem for your engine.