You can chop anything off the top and you wouldn't need to root prune at all. If you root prune, however, it's a good idea to take some off the top. When you say,
Im wondering how much I should take off this spring before the leaves come out.
, you need to specify what your intentions for the plant are. Are you going for a bigger trunk, branch development, etc.? Also, is the plant in a bonsai pot or is it still developing in a regular pot or in the ground? The last thing that might help could be a picture and specify where your trying to go with the plant altogether.