I am not a fan of totally changing the sky, I will just say.
We do a lot in how we process photos now a days to enhance an image, in most cases to make it pop more. But there is that realism that is still at the core of what most of us Landscape Photographers want to retain. To totally change the sky throws that realism out the window I think.
Everyone's different, but I know I couldn't do it. In Ben's case he used a layer mask to keep all of the stars and only wanted to replace the background sky behind the stars to make it darker I think? I did it once to try out Sky Replace, but mine was a totally blue sky that had gotten banded for some reason, so I wanted to see if it the Sky Replace would replace the sky with another blue sky. And the end result in mine was it looked identical minus the banding.
Jameel, you aren't the only one to have tried this, so you aren't alone in this. I just want to be honest that for some reason the whole idea makes me queasy. I am not trying to be holier then though either, it just doesn't sit right, and I would not be able to do it.
Although as I think about it, I know for Let's Play when we were doing that, I wasn't bothered when skies were replaced. So I am trying to figure out what's the difference. Perhaps because it wasn't my image?
Maybe finished images like this need to go into Digital Art instead of Landscape? I am just thinking out loud as I don't know. And it could just be me, and I don't want this to come across in a way where I am saying what's Right or Wrong or admissible. As artists we should have freedom to create our art.
Now on to your photo. I am not sure it needs to be flipped as Alan says. For me, the ground appears a bit too bright for the sky. So perhaps pulling down the midtones on the ground a bit to darken it and give it a more of a sunset feel?