Driver for hire... what to charge?

[EJXD2]

Someone has offered me a gig driving her SUV 800 miles so that she can fly but still have her car during an extended vacation.

She has offered to pay expenses, my return flight, "plus whatever else I need," meaning she's looking for me to ask for money for my time, but how much?

The whole ordeal should take about 30 hours, so $300-$500 plus expenses seems fair. Any thoughts?