I think you are losing or have lost the oil pump. You probably should not consider the car driveable until repaired, because you could do more damage through not having sufficient oil pressure.
Someone more familiar with your engine can help you with the specific questions. I think on some of the 300 series cars in the '80s there were two sections on the oil pan, one of which can be removed while the engine remains in place to change the oil pump. If that's not the case on the 190 series then you'd be lifting the engine somehow.
Good luck - your wife did the right thing - tell her we said she is smart!