It's real easy to remove them...I just did it. You want to remove the whole half shaft as a unit, and then do the U-Joints after it's out of the car. All that takes is 4 little screw bolts on each end of the half shaft. I think it is a 1/4" 12 point socket. You might want to take a wire brush and try and clean the bolt heads so that you can get the socket on there nice and snug.
I don't know about changing the actual U-Joints themselves, as I brought them to a Corvette shop (Corvettes Unlimited, Long Island, NY), and they pressed them in for me and sandblasted and painted the half shafts. They look great!
When you're putting back the half shafts, make sure you don't knock off the end caps, as they have many little bushing/bearing things in them, and they are a pain if they get disturbed. Also, you will want to use the medium (blue) locktite on the bolds when they go back in.
Let me know if you need any more info...I just did a complete Offset Trailing arm install.
Good luck!
- Jeremy