Well, like we have been trying to tell you, get a gauge on there. That means unscrewing the old sender and screwing a gauge sender/adapter in its place. You have raise the car up a bit (ramps or jack stands), look for where the oil drain plug is on the oil pan then go up and to the left a bit. It will be below the head and somewhat to the left and above the block drain plug. There should be a wire attached, although mine has been known to work lose (when the wire is off the light will *not* light up ever, so I assume yours is still connected). Access will be a little tight, but you need to unscrew this and then replace it with a gauge sender. If you get a friend to drive you to walmart so you can get a $7 gauge then instead of a sender you will have a little fitting and some adapters. Find out which adapter has the same threads as your original fitting. A polyethylene hose fits in there like a plumbing compression fitting. The other end of the hose goes to a compression fitting on the gauge. It's in the instructions.
Yes, when you get the gauge hooked up you will not yet know if your sender is bad. It is at this point that you will start the car and run the diagnostic described above, noting the idle oil pressures that Jeremy provided. If your oil pressure is reading normal on the gauge then your sender is bad. If your oil pressure is low then your sender was correctly telling you to stop the car the whole time and you will need to fix the low oil pressure problem.
I hope this helps.
Rick