Although the common flavor you hear about being associated with duck is orange, it is plum that is considered the classic flavor combination. I also once did a roast duck with blueberry that I was very happy with.
However, as someone has pointed out already, you really don't need a fruit sauce or side to go with it. In fact, duck is really quite nice on its own, as the foxes in my back yard will attest as they pick out the feathers from their teeth that they got from my 4 muscovy ducks
About the fat: cut some hash marks into the breasts of the duck. If you are roasting it whole, drain the fat out after about 20 minutes to half an hour. If you are cutting pieces off, then render the fat off the breasts by cooking them at a low temp in a pan fat side down for a few minutes. The French refer to duck fat as liquid gold, and they make the absolute best French Fries. Talk about the perfect side dish!