Q: What issues would I have if my oil pressure switch is bad

Oil pressure switches can develop external leaks (that is, they can leak oil onto the engine) and/or the switch can fail internally such that the switch either fails to warn of low oil pressure or the switch goes off prematurely and illuminates the oil pressure warning light when in fact nothing is wrong. However, if a problem has been detected in the "switch circuit" that includes the sensor, such a problem can sometimes be wiring and terminal related and have absolutely nothing to do with the switch itself. Switches can be tested, although they are relatively inexpensive and so they are sometimes just thrown out, for sure if they leak. Switch diagnosis and replacement can be requested. You can also obtain, on a mobile basis, right at your location a check engine light diagnostic. The responding mechanic would download the diagnostic trouble codes that have caused the check engine light to illuminate and identify the faults that have caused the codes to set.

The oil pressure switch only controls the oil pressure indicator in the instrument cluster. If the oil sender went bad then you would not see the oil pressure indicator on the dash come on if you turned key on with engine off or if the engine got low oil pressure if it was running.