Re: The Hand
You might try using a Hue/Sat layer set to "Color" blending mode, in the Hue/Sat dialog you will find 3 eye dropper icons. Click on the + eyedropper icon and then click on an area of color within the hand that you want to change, now click on the - eyedropper and click on any areas that have good color you want to retain. Now go to the Hue slider and make it -180, this will look bad, but it will show you where the color selection has been narrowed down to and what the layer will be changing. If the changes are to broad, grab the - eyedropper again and keep clicking on good areas of the hand.
This method may not work to well based on the image you posted as the colors are all pretty similar, but its quick to try and may work, remember to create a mask just for the hand or to include other areas with similar color problems.
Another way would be to create a new blank layer and set it to "Color" blending mode, then grab the brush set to a low, 5%-20% opacity, and sample good colors of the hand. Now you can paint in over bad colored areas on the hand. You will want to also do a bit of D&B below this Color layer to match the tones with surrounding skin.