As regards the door reconstruction, SoCalSecrets, what can I say? I'm just naturally detail-oriented. Perspective is a
bear, especially for people like myself, who can't actually draw.
For whatever it's worth, I rarely if ever increase saturation on a selective basis, because it's very easy to create an artificial effect. If I
do want to selectively fix an area of an image (to adjust hair-colour, or fix blotchy skin tones, for example), I use GIMP's
Select Region By Colour tool to create a mask, blur the mask a little to avoid hard edges, and then apply the change "through" the mask.
The most common cause of greyish, unsaturated colours on original cover scans is the overall
tone distribution. That's usually the first thing I fix on a cover after resizing it to my standard 500px width. See
my posting on Tips & Techniques for details. Beyond that, I usually adjust colour saturation for the image as a whole, unless there's some
gross imbalance in the original image.