The oil pressure sending unit on a 1992 Oldsmobile Ninety-Eight Regency with the 3800 TBI engine is located on the driver's side (left side) of the engine block, near the oil filter. It's a relatively small unit with one or two wires connected to it. You might need to remove the oil filter or at least move it slightly to get a good look. Be prepared for some oil spillage when you work in that area.
It's best to consult a repair manual specific to your vehicle year and engine for precise location and removal instructions. A picture in a repair manual will be invaluable.
