Use the search function for E420 / 400E differential and you'll get more info. I believe that I've read 4-5 hours (if you're doing it yourself, for the first time). Shop could do it in 3-4. I also seem to recall that you'll need to but the magic box to install behind the dash so that your odometer is corrected once the new diff is in.

I think you'll use your existing diff. cover instead of the one that comes with the 2.82.

Hope thsi helps.

Troy
1995 E420