Any really good body man can probably tell you if your car has had body work.

Some clues -
Paint on parts that were not painted
different fastners on one side, for example, screws instead of rivets
damage to wheel liners or suspension pieces - since people do not see these parts, body shops often do not change them.
a lack of stone nicks on the front of the car or on the windshield
a new part on one side of the car

Take a good look on both sides from a distance, look for ripples, flat spots, etc

Measure the diagonals from the front corner of the windshield to the oposite front corner of the engine compartment, they should be equal. A body man may have a book of these measurements. (I have a set of 240 manuals that show several measurements to take to see of the body is straight)

Take care in confronting your dealer, you will probably do better with him as a partner than a foe for the next two years. If you have real bad luck, he may help you with your next car.

Try to judge the car by what it does instead of your fears, you will enjoy it much more
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3 8s & 2 7s 725,000 miles total