Otto....
I say go for it - do a little research and see what you find... Look for cars with low cD values and start there....
But, I agree with SteveP. It's important, but look at the relative impact. A sailplane is, as Steve said, highly optimized in it's current condition. No doubt, much of their aero problem spots come from their leading edge. As cars are bluff bodies (exception for basjoos perhaps), the trailing surfaces have a much higher significance. Sailplanes are not bluff bodies - which is why their leading surfaces are more important (ditto for solar cars, velomobiles, submarines, etc.).
Now all that said - just because I agree with him... That's not me saying not to do it. If you've got an opportunity to clean something up - I say go for it. You'll no doubt make a difference
