Under no circumstances would I allow the dealer to wash or detail my car.
Their polish they offer you is going to make things worse. Have them reimburse you for a quality job somewhere else.
They'll let some 19 year old kid making $9 an hour 'detail' your car. He'll polish it using the same wool buffer pad he's 'polished' 30 cars with that week, and probably end up etching the shit out of your clear.