How much to repair the shift differential leak? on 2004 Jeep Liberty

My Jeep has been awesome - I'm not complaining. I've had it for going on 10 years and it has over 170,000 miles on it - so I expect some necessary repairs. I had the idle and bad start-up problem - it was a coil system in the spark plugs and all were changed & problem gone ($287). When they were repairing that, the guy said I have a pretty bad leak around the pinions in my shift differential (hope I repeated that correctly). He quoted me between $800-$1100 - does that sound right? Seems like alot of money to me!

Asked by for the 2004 Jeep Liberty