Moving a young apple tree in early spring?
Definitely not too early. The best time to transplant any tree is during late winter while the tree is still dormant, well before bud break in early spring. That reduces the shock of transplantation and, if done early enough (say, January), will give the roots time to get established before the growing season starts.
Early bloomers, like Nanking Cherry and Forsythia, are already budding in the Denver area, so the ideal transplanting window may have closed already for this season.
That said, sometimes we have to push ahead whether the timing is ideal or not. If you decide to move your apple tree now, get as big a root ball as you can manage and follow the advice for planting a tree in PlantTalk Colorado #1711 'Planting Trees & Shrubs' found at http://http//www.ext.colostate.edu/ptlk/1711.html. That PlantTalk will link you to additional helpful information about planting trees.