1995 Buick Lesabre oil pressure switch

I'm considering buying this used car. But I'm concerned that the oil pressure is registering low on the oil pressure gauge and when ideling the red light comes on. When I'm driving down the road the light does not come on. Someone told me that it may be the oil pressure switch causing this. What other things could cause this problem? The car has very low mileage and it seems to me with no more wear on this engine due to the low mileage souldn't it have very good oil pressure? If I replace the oil pressure switch and it doesn't fix this problem how do I determine what is causing the low oil pressure?Also where is the oil pressure switch located on the engine and is it hard to replace?Thanks Sherry