cutting back an arborvitae
 

My newly purchased house has two large (15') arborvitae trees in front of a small front porch. They are so large they block out any light in the front windows, and porch. A landscaper recommended removing them and replacing with some boxwood. The trees are healthy, and I hate to cut them down (not to mention the expense of hiring a landscaping company.) Is there any way I can cut these back significantly (almost by half)? Would it be ok to trim back a few feet a year? Or can these trees be "topped" all at once to look more like a shrub? What would be the best tool to use? Is it too late in the season to do anything this year?(I live in North Eastern U.S.) This is my first house so I'm totally new to this. Thank you so much for your help!