So they're selling parts to cars they dont know two ****s about, and you find that acceptable why? Some parts are easiest and most convenient to get at a dealership, have no part number, and spending half an hour trying to describe the $4 part you want to a salesman who cant tell an Impreza from a Tribeca is an experience that'll likely turn you away from going to that dealership ever again.
If you sell cars, know about the cars. If you sell parts, know about the parts--that means you have to know about the cars too. Simply knowing how to use the computer to look up part numbers is not good enough.