Three Orings (Carolina BikeandTrike - five pack), moly paste, waterproof grease (Guard Dog or Belray). A bunch of rags, stiff brushes and solvents in a pan to clean out the old goop (Nitrile gloves are a very good idea with this).
A quart of 80-90 or 75-90 synthetic rear end dope for the pumpkin.
A 27mm axle socket.
Maybe a new Ujoint boot.
A strong back.
A big dose of patience (
and colorful language) with the Ujoint boot.
With any luck, you won't need a Ujoint, drive shaft or pinion cup. If you need any of these, and don't have them, you'll not ride till they are delivered.
Besides the link to ChrisJ's how-to above, this link with pics is very helpful (clicking each pic makes it big with extra instructions)
http://www.rattlebars.com/mtz/ujoint.html