Plant now, before the buds open.
Move with as much root ball as you can. Plant in a square hole as roots can break out of a square hole easier than in a round hole (advice from Kew Gardens). Round holes encourage roots to grow around the inside of a round hole, whereas in a square hole when the roots encounter the corners they will break out and into the surrounding soil giving the tree more stability.
I hope this helps, if it doesn't at least it gave you something to read. ;-)