@browncoat - Hiring a professional is no guarantee that the work done to your trees will be good. Or maybe I should put that differently. Paying someone doesn't mean you'll get a professional.
Tree trimming doesn't have to be that hard, depending on what you want to do. Research can get you a long way.
But if you need to hire someone, particularly for dangerous work, make sure to ask around and get someone who does good tree landscaping and can communicate with their clients. When my parents went to get a small passage cut in their trees for a telephone wire they ended up missing a few trees which was not the intention.
But, once they are gone, they take forever to grow back, so be sure you either know what you are doing, or find someone you can rely on to do it for you.