Have you contacted an arborist in your local area?
If it happened this year, I'd say wait until next year and see if the tree recovers. I've transplanted many pine trees and the shock makes them loose many of their needles. I've learned that mother nature takes her time in fixing things. Many trees that are root shocked come back. Patience and a bit of tlc with some fertilizer around the perimeter of the root ball, it might come back. Otherwise, that part of the tree should be removed. It might look a bit odd, but in time one of the tree's branches will assume the dominate leader position. The last step and most drastic is to just cut it down and replant. Watching a pine tree grow year to year is a beautiful thing to see.
Woodwork Safely,
Jim Barry
www.WoodchuckCanuck.com