You can also plug the hole in the yoke with an aluminum rivet instead of welding...just an alternative.

Your rear seal is easy to replace...you can take off the rear housing of the transmission to get better access to it. If you do, there is a sleeve that the driveshaft yoke goes into on the tailshaft. It has an o-ring inside it that can be changed as well (this is supposed to keep the weep hole on the yoke dry).

All still simple stuff that you can do at home...

If you have a welder, Red's way is probably quicker!