Go slow and be patient with that front cover. They are all very hard to remove, even the first time from when Ford did it. Just keep searching around the cover for places to pry up at, and to tap a screw driver in the seam of the cover and case. It may end with some gauging of the cover or case, but it should be reusable if you don't go to hard at one spot.
@410Fortune, Jamie; have you ever considered installing a drain plug on the front cover? I want one so I can drain and refill it without waiting to drop the diff.