Yakima and Thule are the two brands you want to look into. If they aren't available yet, throw it in the trunk for now. But I think they're out now.
They're not hard to put on or take off. Some people put them on and leave them on all year so they can think they look cool. The ones for the 3 should have 4 rubber bottom "towers" that mount at each corner. These will hold the bars that can hold a variety of configurations. Then there will be some kind of rubber coated bracket that will fit the door frame. Tighten it down and presto. The first time is the hardest, but then to take it off, just loosen it a tiny bit and it will come off. When you put it back on tighten it just a bit and presto again. A couple minutes is all you'll need. I wouldn't leave it mounted because there can be quite a bit of wind noise, not to mention hurting your mileage, but this is probably pretty minimal. They do make fairings for the front of the rack. These help to direct some airflow over the rack cutting down on noise.