I don't know if the dealership would cry about you changing fluid yourself or not. I guess it would be ok if you had receipts from the lube lock and fluid. something as evidence that it was indeed done if an issue were to occur.
check the bolts like 4jeepin mentioned. I've banged my rear diff cover being an idiot driving and knocked a chunk of rust off
it managed to disrupt the gasket seal and it leaks. as long as you aren't seeing drips or a puddle on your driveway from it, other than tightening the bolts, I wouldn't pay it no mind. they need done every other oil change anyway, so no sense in dumping expensive gear oil out the window just to reseal a gasket.