The fluid getting changed shouldn't have make your diff leak. I know that there is a gasket specifically for the pumpkin, but when I was changing mine I couldn't get a hold of one so I just ended up using some gasket maker. It's been nearly half a year with no signs of leakage. Of course, to take it apart just to change a gasket is a lot of work, but not difficult. If you don't mind getting dirty and have most of a day to kill depending on your skill, you can replace it pretty easily.
-1992 4Runner (Medallist Edition) Still given 'er 16 years later
-Santa Cruz Bullit