Yes, the window awning is rolled up manually. Dealer installed it came to just over $500. If I'd done it myself, it would have been $111 less for the labor. The rest was the awning, arms, and shipping costs. It was in the shop for some warranty work and maintenance, so it was easier to let them do it. The size of the window length is the factor in how much it costs. Mine is a fairly long one to cover both windows. Your's may be somewhat less.
The greater value of that awning for us is cutting off late afternoon sun at our site. We could not sit at the dining table with the shades up without it. Reducing the sun load on the windows also helps keep it cooler inside. We are not groping around in the dark, either, but ours is a larger coach with more windows, including the big rear window. It would be doable, but perhaps seem silly, but you could put a window awning over the one under the main awning, as well. It looks like there may be enough space. The awnings come in a variety of colors, including white. I think Carefree had some that may even be more of a mesh to allow more light.
I am surprised that your 28' trailer only has a single roof vent. We had a 27' TT, a SOB, that had two roof vents, one in the bath and one in the bedroom. We also had more windows than I can see on yours (some were jalousie, also). Even so, on hot, humid Michigan nights (we get them), it could be very uncomfortable without the A/C on. And some small desk fans, too.
Ours is also an electric awning and does not have adjustable arms. But it has yet to collect so much rain that it's a problem. It seems to have a natural angle towards the front of the rig, with the rig level, and drains off that end. You do have to be sure to extend it as far as it will go without re-rolling itself. Some folks tie theirs down and hang lights with no problem. Problem comes if a storm brews up and you need to bring it in quickly. We've taken to using battery-powered lanterns with timers on large plant hooks on the roller at either end. I can get them off fast and bring it in if needed.
I don't know why they don't offer a choice of windows, even though it would add a premium to the sale price. But we've owned the BH since late 2008 and haven't stop spending on it yet. Some say a boat is a hole in the water you toss money in. These rigs are more like platforms on wheels you pile money on. Unfortunately, it blows off as you go down the highway.