Have you tried Sony's online support or just phone? I only exchanged a couple of controllers before they went out of warranty, but I did it online and the rep couldn't have been more polite and the process went smoothly. Not saying it would make a difference because you're going to find both good and bad reps on any avenue, but it might be worth a shot.
I will say it seems like you might be expecting more from the Sony Store folks than what they can actually do.
Hope it works out for you though.
FYI
, there's a manual eject for a stuck disc, just in case you need to get a disc out before sending the system off.