Hi Trevor - I am certainly no expert in PS but there are some easily assessable websites with good tips on processing astrophoto's. Some of the ones that I think are worth looking at are:
http://www.ezystyles.com.au/photoshop.html
Processing with Photoshop CS2 - Adjusting Levels, Curves & Colours - by Eric Lo (member in IIS)
http://www.astropix.com/HTML/J_DIGIT/TOC_DIG.HTM
Digital Image Processing by Jerry Lodriguss
http://www.starrywonders.com/tutorialpage1.html
Image Processing Tutorial- by Steve Cannistra
Also the book "Photoshop Astronomy by R. Scott Ireland" is very detailed and with tutorials. I am still trying to get through (and understand) all of the chapters but so far it has been great for me. I purchased my copy from Bintel (You could probably get from others and online if you looked).
I am sure there are many other tips/hints out there as well.