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Front differential on my Cadillac Escalade? - cadillac escalade repair power liftgate

I have a 2002 Escalade, my wife and I just bought. Bringing It Home 2 days after binding experience where you turn left or right. I took it to the dealer and of course, is sold as is, but they are willing to help with the costs of repair. So my question is: How can I expect for a new front differential needed or pay? Thanks in advance