Hi,
How would you seam a shoulder where both parts are moss stitch. I have found this video: http://youtu.be/4tHKw69dE7E but I can’t see clearly what they mean when they say they go through a knit and go out in the purl…
I’d use the same basic technique as for horizontal stockinette seams. See if this tutorial (toward mid-page) is clearer. It’s ribbing but it’s the same idea as for seed or moss stitch.
http://www.studioknits.com/bookpage66.htm
Also, this may help although it’s stockinette.
Wherever I can, I try to use 3 needle bind off at shoulders because it minimizes the seam and is so sturdy but that may not be convenient for you.
Not too bad for the first time 
Looking good! You’re our go-to expert.