Help! Landscapes, color theory, and digital painting techniques?

I've been attempting to practice landscape/environment painting, and with that I realize that I need a better understanding of color theory.. and maybe even some digital painting techniques that professionals use.  I'm at the stage where I suck so bad at environments and color that I generally want to quit early on because it's so frustrating.. but I know quitting only leads to NO IMPROVEMENT. lol

Could anyone give me some advice?  Techniques?  Books?  Dvds?  Videos?  ImagineFX articles?  Useful brushes?

I use Corel Painter 12, the scratchboard tool, and a blender.. every once in a while pulling out the oil brush.  I'm sure any kind of brush can be applied to any program.. what would you recommend?  Whats your workflow for painting?

I'm unsure of how to go into great detail on any of my pieces also..

I'm working in black and white first because I'm not confident enough to work with color AND value at the same time.. though I don't want to continue like this for much longer.  If I do continue like this, how can I work on the value and then use layer modes to add color into that? Seems like I use layer modes and the colors don't match at all. Should I just go over the black and white with more saturated colors slowly?

Here are a few of my recent studies.. I kind of feel like I'm hopping around blindly until I get something right, and I hate it.

First environment sketch and some notes from Practical Light and Color by Jeremy Vickery:

My most recent studies:

Some things that have helped me get to this point recently:
Practical Light and Color by Jeremy Vickery (Gnomon dvd)
Color Theory:  The Mechanics of Color with Richard Keyes (Gnomon dvd)
This ImagineFX tutorial from Issue #31 on the subject of colour!
And I've frequently watched these Feng Zhu videos.. lol
http://www.youtube.com/watch?v=xCmz3XuS6TI
http://www.youtube.com/watch?v=wy9MMdzbWcw

Any help would be GREATLY appreciated!