To goodwill: blending basics

[sandpiper]

Rajeev, here's what I did
in Photoshop, open the two images and make a duplicate of the one exposed for the buildings
on the duplicate image, select all the bright overexposed sky with the select tool
on the 'sky' image, use select tool to select the sky area copy the selection
on the duplicate image paste the selection as a new layer, then in the blend option choose darken and then all the bright sky are is replaced with the correctly exposed sky
move the copied sky around until its where you want it, then adjust the levels to lighten it slightly. When happy, from the Layer tab, merge the two visible layers. There will be some artefact around the skyline and this can fixed by carefully cloning from the original image to the duplicate image.
That's basically it, then it just takes time, patience and practice to get the result you desire.
cheers
Chris