Wow.
While the changes to the image appear to be quite dramatic, in fact all you’ve done is alter the sky and the image still appears believable.
Overall I think the image and the changes are very strong. The introduction of oranges, reds and greens in the sky help give the photograph a dramatic edge.
The composition is very strong and you’ve used the foreground tree to create a “frame within a frame”. However, I do feel the horizon is a little too centered. With such a vibrant sky you might want to consider changing the composition or cropping the image to include less of the ground and more of the sky. This will help give the image a more informal balance and help intensify the dramatic look to the framing.
The only other concern I had was when I enlarged the photograph. The area to the right side where you’ve done your Photoshop editing isn’t hidden enough. There are some railings that appear. I would recommend either removing them or editing your foreground layer so when we look through the railings there is more continuity between the blacks in the layers.
Right now, when I look through the railing, I see various shades of grey, but your new background image has strong blacks. There is a consistency issue to look at there.
Other than that, this is a great photograph!
Keep up the great work.