Why did you change out the injectors originally? How much higher than full is the fluid mark on the dipstick? How much oil did you add during the oil change? I understand you checked the oil level after the change is this right?Did you checxk the level off the old oil before the change? Plus if so was it normal.

What is going through my mind is that even if the O ring failed in the lift pump it should take some time to pump a lot more fuel into the crankcase. Thats why I asked why you changed the injectors.

The only other place I can think of that has a major interface between the oiling system and fuel is inside the injection pump. Although I never remember a case of a failure there it certainly has a better chance of adding a lot of fuel to the oil faster.

At least from your descriptions so far it does not sound like you destroyed the engine.