How bad could it be?

Car Details:

1999 Acura TL


~123k Miles

2nd owner

A few days ago, I made the mistake of letting my friend drive my car to come and pick me up from work. I should have known to just wait for the bus when she asked me, “What gear do I drive this in?” I simply answered, “D4”, the position for normal driving. When she picked me up, she mentioned that my car “shifted funny” and my fears were confirmed when she had told me that this is what she had done:

I have the “Sequential SportShift Mode” option in my car, which just happens to be just a shift over to the left from “D4”. Even after my telling her to drive in D4,she second guessed her position choice and shifted over to sportshift mode for the last mile. She said that for that last half of the trip, didn’t get over 35mph (if this is even possible without shifting up?). The service light turned on the day after and my car starts and runs a bit rougher.

My question is: how badly is my car damaged due to my poor information that I gave her and her lack of knowledge of my car? I am due for an oil change soon… could the light be coming on automatically for that? How much will repairing any damage be?

It could be as simple as an over heated spark that occured during her transmission test. The plug could be fouled the spark is dropping out.