Nice image - I think the replacement sky is well done, but too dark for the lighting in the scene - try quick selecting the sky, copying it to a new layer above the original {CMD/CTR - J], setting the blend mode to Screen, with an opacity of about 75%. The detail will still be preserved, but the lighting will look a little more consistent with the combine and field.
The detail in the image is nicely rendered - it may be able to stand up to a little more global contrast, if you wanted to move toward that look. Try a levels adjustment with a black point of about 13 and a gamma (midpoint slider) of about 0.85. This will reestablish the sky and the combine contrast together.
kirk