From the picture it looks like your carrier is probally ok. It only looks like the the pinon cut into the outter wall of the carrier. IMO

 

I'll take that busted carrier if you throw it out.

 

I've seen better pictures taken by a 4 year old with a Fisher Price camera. The only thing I can tell looking at that picture is that its a rear diff. If the guy wants anyones opinion he should take some decent pics...

 

Sorry can't tell from Red-X

 

No dealer can void your warranty. They can refuse to cover a repair, but they are required by law to prove that your modifications caused the failure, or created a situation that led to the failure.

So, regardless of whether or not the dealer believes that your mods are the cause, I strongly suggest that you call Chrysler Customer service and discuss this with them. Hold the dealer's feet to the fire. For every dealer with skilled mechanics, there's another dealer who could not diagnose wet feet after peeing on their shoe.