I wouldn't waste my time taking it back to the guy that screwed up the initial installation and then offered half baked excuses to cover up his ineptitude .
If you attempt the repairs on your own..... Deve's tech article might make it easier as his technique does not require removal of the torque tube to replace the ring and pinion gears.
http://www.devestechnet.com/home/DifferentialOverhaul.
