The color of the sky compliments the building nicely. There is one lighter spot on the right hand side of the sky. It might be natural, but it does kind of draw your eye to it. But that's just me picking. Looks great!
At first I knew it was photoshopped but then i though, it really adds to this shot! The orange contrasts nicely with the beige building, and there are no imperfections in the sky besides the one light flare, as woodsac mentioned draws your eye. Great shot!
How did you find a Photoshop class? I really like the way you did this. I think I mess my photos up worse in Photoshop , because I really do not know how to properly use PS.