Buying a used rear end what should I look at to see if it's in good condition????

Hey guys , found a rear end on Craigslist . 8 3/4 741 case posi with 3.54 gear in it that I wanna pick up . The guy wants 450$ for it , supposedly it's got 1000 miles on it . I was wondering if that's a fair price and what do I need to look at when I go to check it out , so I don't buy a busted rear end Haha?

Thanks
Peter