1) The survival rate is high if you make the right preparations.(ie.
proper hole depth, width, peat moss, topsoil, fertilizer, etc)

2) The best time is in the fall when the tree goes dormant.(you never
want to expose bare roots during its active growing season)

3) If you are going to hire a landscape contractor or even better, an
arborist, they will definately have the equipment to dig up a tree this
size. They also should also know which roots to prune and which ones to
keep.

4) I am guessing this tree is 4-5 years old. Depending on how long
you've had it in the ground, I would say that the roots are pretty
deeply established. The labor to dig up and transplant this tree will
definately cost more than twice as much as buying a nursery tree and
planting it yourself.