A friend of mine as a joke painted grafiti all over a beater that I drove to college. I did not care about the grafiti but some of it was "offensive" in nature. I was able to use mineral spirits to remove the spray paint with really good results. My friend was really annoyed to see his nice paint job that he had spent so much time on completely gone.

If your detailer is careful you should have no problems. You will have to rewax the car as the mineral spirits remove all of the wax. Depending on your paint job you might see an improvement in color and shine if he strips the whole car. Do make sure he is insured though because clear coats are quite thin and fragile. A little too much solvent and its time for a spray booth.

Speaking of clear coat I am wondering if you can use solvents like this to remove a clear coat. I have a spot on the hood of my Volvo that I have been waxing like a fiend and the dull goes away and comes back a few months later I know that the real problem is the clear coat is going. If I could have the clear coat stripped and resprayed it would save repainting the whole car.