It would be possible to cause an oil leak while replacing the water pump.
water pump, oil, water, engine coolant....main cause would be engine coolant, just check to see if you have a leak.
A major leak.
A bad intake manifold or manifold gasket can cause water to leak into the oil. Some newer cars have plastic manifolds and they will crack from age.
If the thermostat was not installed correctly, the housing can crack but it would leak engine coolant not oil.
can exhaust manifold leak cause you to burn oil
oil tanks in ships may leak
I would not expect a valve cover leak to cause a car to stall. A valve cover leak can fill the spark plug area with oil which can cause rough running.
engine oil leak
An oil leak is always going to be out of the engine as the engine contains oil and the car does not. I think you are saying you are loosing oil with no apparent leak. If that is the case the engine is burning oil and that is why you see no leaks.
Changing the plugs and plug wires correctly has nothing to do with nor can it cause an oil leak.
No