The Whirlpool Galaxy

Putting this together is very similar to the Lagoon Nebula.  There are only very minor changes that need to be made.  Since this particular image is slightly less exposed, rather than putting it in Log for, put it in Log Log from since it is brighter and will make things stand out more. 

Also Galaxies are best for using different tools such as the dodge and burn tools.  Use the dodge tool to brighten up the center so attention is drawn there.  Another good tool that works very similar to it is the sponge tool.  It brightens things up well, and if used in different filters, it can make colors stand out more in some areas then in others depending on the desired look of the image.  The burn tool can be used to give the arms of the galaxy shadows and make the image seem less two dimensional.  Just use a smaller brush so the detail can be made more precise.

For this particular image the burn tool was used in each filter because most of the images were over exposed.  Using the Burn tool takes away the bright parts around it without covering up the stars in the background.