Here's some pics.
This is the assembly between the 2 ujoints. Piece at left is welded to the drive shaft. Note: ujoint installed in this pic.
Here's a close up of the centering stud and shaft end yolk.
The shaft in the above pic rides in this hole in this ball, it's packed w/ needle or ball bearings (cant remember which) and grease. When damage occurs, it's usually the bearings, but if you wait too long, the shaft or ball will start to wear. In worse case, they have to weld on a new yolk w/ centering shaft on the end of your drive shaft. I was lucky, that part was good, only need a new ball w/ new bearings, marine grease was used all around.
The ball is in upside down in this pic, but this is what happens when the boot that surrounds the whole thing leaks and crap gets in there. The entire socket is exploded in this pic.
Here is a pic of the ball that was removed from mine. Ted had to weld a piece of scrap metal into the hole in order to pull it out, it's pressed into the socket.
Total cost for 3 ujoints, installed, and the new ball section:$166
Here are some pics of the entire repaired part: