New fuel and crankshaft sensors, engine light?

Recently I had trouble going uphill and getting any real acceleration. Particularly after a red light. It took a minute to get above 20 MPH Saturday. It drove fine the day before and seemed okay a few hours after the issue as I was dropping off at shop. When Monday came around, they said it drove fine, but the computer flagged the two sensors (crankshaft and fuel).

It seems to work great now. Even more responsive than I remember it being in years. But the check engine light is on now. There hadn't been lights on prior to going into the shop. A tech said wait 48 hours to see if it goes out. Said carbon needs to burn off or something?

1). Do check engine lights tend to persist a few days after these sensors are changed?

2). How long after these sensors start to fail would a driver even notice a difference?

3). Does harm to the engine itself only happen after the driver notices a lack of response? I am worried it was acting up longer than I could of known and needless harm happened.

I had car in for inspection only a week ago so I assume this is all pretty recent and computer would of caught it then if it was malfunctioning then.