I'm a very very new beginner (nerdy wave).  Essentially, I've seamstressed for ages, and about two months ago decided to play with leather for a change of pace, and I'm finding it a great medium (no grainlines to worry about--sign me up).  A week and a half ago, I got my first carving tools as a birthday present, and I've been experimenting all week on a piece of hide. 
What I'd like to know is, is there a way to take one piece of leather and soften it in some spots to make it more pliable, or to take a pliable piece of leather and stiffen it up in places?  Would a treatment like that affect dyeing later on, or would it be done post-dyeing process? 
Additionally, I did dye my first piece of leather today and there were areas where the leather resisted taking the dye as well.  Was this just a result of my not having the best leather?  Can I get something that can make the leather more receptive to the dye? 
Also, if I post some of the things I've been working on, how constructive is the criticism?  I'm sort of experimenting with things on my own, I just got a fifteen minute demonstration from a nice person at Tandy about carving who sort of gave me the four tools he thought I'd need and I bought them, and a 20 page pamphlet I was sold, so I could use a little mentoring at this stage.