I have just finished one side of my shift, and I saved the other side in order to put together a small tutorial on setting a sleeve gusset. Setting the gusset is not difficult, but it requires careful attention to the "order of operations" -- things really need to be done in the correct sequence. People learn differently and I know I would have had my "ah ha!" moment a lot more quickly if I could have seen how the pieces went together in three dimensions rather than staring a line drawing. I hope this helps!
Here is part 1.