Welcome to the forum.
Brake replacement varies from vehicle to vehicle. If you think there is a rock try backing up and apply the brakes with some force. That will sometimes clear stuff caught in your brakes. I have had a noise occasionally after driving on the beach and what I do is find a large empty parking lot, back up at about 15 mph and then apply the brakes with a good amount of force. Do it a couple of times, it may work.
$600 seems like an awful lot of money for just the front brakes. The parts for replacing the pads and rotors on all 4 wheels is $435 from my dealer. I inquired recently because my Latitude has 87K miles on the original brakes. Just had them checked last week and they are still in good shape.
Was it the same dealer that said you needed front brakes and then said the brakes checked out ok?