+1
It isn't worth it to do it yourself, unless you have two 20-something sons you can force to do the work.
+another 1...
5/8" sheetrock, at that height, is very difficult to work with, even if you have a team of guys and the best drywall lift / scaffolding that money can buy.
When I built my 24x36, which has a "cathedral" type ceiling, I did all of the drywall work myself...
except for the ceiling.
A local guy charged me $800 bucks to supply the rock, hang it and tape it, ready for light texture (which I did later). He also did the "triangle" sections at each end.
They (team of 3 guys) did the whole thing in 12 foot long sheets. In one day.
If I had done it myself it would have taken me a month of Sundays, immense amounts of back pain, and probably would not have come out nearly as nice.
And, I'd now be trying to get rid of a $400 drywall lift (forget about using those $149.99 lifts for a job like this, it ain't gonna happen)
Think long and hard about how much money you will actually save, and whether it is truly worth it.