Preferred time of year to trim fruit trees.
Adams County Colorado
The very best time to prune cherries is the early spring before the plants leaf out. Minor pruning could be done now but for major pruning like you describe waiting until next spring would be preferable.
You can find more information on pruning fruit trees here: http://cmg.colostate.edu/Gardennotes/771.pdf
I hope this helps, please let me know if you have further questions.