On the oil change, I think it depends on the future of the car.
If she is likely to keep this as a long term car, my thoughts are oil changes every 7500 miles. Based on what data I have seen on M1, that is when it starts to go south.
If she is a three year owner type, this is over kill and the 20K is likely OK.
On the weight issue, I think the 0-40 is fine. However, if it were me, I might run Castrol 5-50 in the South.
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