I know there is a star case on the coolant sludge issue, if that's indeed your problem I think Chrysler is covering it all & replacing everything under warranty. I'm not a fan of the dealership myself, but it might benefit you to have it documented & have the heater core, etc., replaced in case you have issues in the future. But I get not wanting them to tear it apart, especially if you have the ability to do it yourself.
I've also heard that they are having issues with the blend door being broken. But if you've seen the sludge/sand I'm guessing you're not so lucky!?
So far I'm lucky, I had to have my coolant & tranny hoses replaced under warranty so they did a flush early on & I haven't had any sludge issues. Yet. She's a bitch tho, I won't be shocked if it happens.
So far (28K miles, 2013) I've had:
water pump replaced under warranty
coolant/tranny lines under warranty
seatbelt under warranty
light sensor under warranty
stress crack in windshield under warranty
heated mirror recall (not done yet, don't use my doors)
it won't shift into drive when in 4L quite frequently - can't diagnose
I've had no brakes 3 times - can't diagnose
misc electronic freak outs, not downshifting etc - all undiagnosable
Those are the kind of reasons I bring it to the dealer. It's such a piece of crap, I want it documented cuz one day she is gonna kill me & I want my family to be able to sue.