Stop Engine, Low Oil Pressure message comes across message center when vehicle stops at a red light or stop sign for 30 secs or more

If you rev the engine does it go away? What is probably happening is that you have damaged or worn engine bearings. These bearings are designed so that there is a gap(clearance) between the crankshft and the bearing. This gives a space for the oil to pass through. If the clearance is too big the oil will pass through too quickly and the oilpump will not be able to build up pressure, even though the volume of oil pumped is sufficient.
When the oil is cold it is thick and the sensor sees the pressure as normal. As the engine oil heats up it gets thinner and that causes the pressure to drop. Also the lower the RPM the lower the pressure. I would suggest you get the oil pressure tested at a service centre ASAP. Also have them test the sensor although sensor failure is rare. Low oil pressure will not just go away and causes more damage the more you drive increasing your repair bill considerably.
I'd say you are already in for a cranshaft regrind and oversize bearings. Perhaps (if you're lucky) only just an oil pump although this is unlikely as bearings tend to fail before an oil pump does. I'd replace both at the same time since the engine has to come out for both these repairs. The cost of having the engine out a 2nd time far outweighs the saving on spares when doing both the first time.

The first thing is to make sure the oil level is full then i would have the oil preasure tested to see if it is low preasure, most times its a bad oil preasure swith, or you can just replace the switch and if the message returns then have the preasure tested and if it low you may have bearing damage or a weak pump .