A front fender is a good idea to keep rain/slush/whatever out of your face. As for a rear fender, I added a rack to my MB instead which was great for carrying bags. A rack and a bag designed to fit it will make carrying gear much more pleasant, keeping the gear over the rear wheel rather than adding panniers which hang out and add width. YMMV
I hope your bike has plenty of attachment points to accommodate the extras. 5-6 miles commute on a bike is very doable, you'll get in shape quickly, don't worry about that hill.