I have the blinds. I ordered my Montana with them after having the less than favorable experience with the day/night shades.
Since Keystone installed them I cannot say for sure how hard or easy they would be to install, but from the looks of them I would guess easy. It is easy to unscrew the fabric cornices. I did that plenty of times repairing day/night shades.
Then just put up the brackets and hang the blinds.
Although I intend to replace my blinds with better quality ones in the future, I must say I really am happy with blinds. I have so much more control of light and privacy at the same time. I like the overall look and feel of blinds much more than those day/night shades. I found it so much easier at night to just walk around the unit twisting that little rod to close them. With the day/night shades it was a pain to "get into position" and hope you could pull them down without breaking one.
I believe you can order the exact sizes you need from Keystone, but I would not do that if the only blinds they have are the same ones they installed in my unit. They are cheap, cheap, cheap.
I do not think you will regret going with the blinds especially if you buy better quality. By better quality I mean even the cheapest blinds they sell at Home Depot or Wal-Mart are better than the ones Keystone installs.