I've done this twice. It's not that difficult and you need to remove the headsail to do it.
They cover the details in the manual (see attached, page 22 of the pdf). But basically it this:
1) untie the furling line
2) tie the halyard around the foil at the "hump" for the insertion point
3) loosen the four allen head screws where the base meets the foil and the one set screw, also allen head
4) remove the stainless steal cage pieces by undoing the allen head screws at the base
5) remove the top and bottom plates, large Phillips head screw driver
6) remove the 4 screws that hold the base to the lower swivel
7) slide the upper portion of the base up towards the "hump" on the foil at the insertion point.
The turnbuckle will then be accessible to adjust.
Separating the upper portion of the base from the lower swivel and remove the four Phillips head screws that hold the two together will be the hardest part. I had to really pry mine the first time I removed it. I used liberal amounts of PB Blaster and WD40 along with a large flat head and a Shark Pry Bar (http://www.amazon.com/Shark-21-2225-10-Inch-Prybar-Puller/dp/B0000224TY).
Another tip is to use Lanacote when you put it back together (another Maine Sail tip). That way it won't freeze up for the next time.
Let me know if you need a hand. I am only over in Hingham.
Thanks, guys. I'm saving these instructions. After checking the mast rake and shroud/stay tensions, I decided to wait and check the forestay at the end of the season, when I remove the headsail. Thanks for the offer, Jesse. I hope to see you on the water.