In terms of what programs you need, there isn't much point in jumping straight in with two feet and then floundering. Photoshop is overkill for what most people need, especially if you're just getting started. Start with something like Paint Shop Pro until you get the basics (and it's a damn sight cheaper!)

As for the texturing part - skin textures are incredibly difficult. Different tonal variations, different lights, and then the seams to deal with. Again, start out with something easy like some freebie clothing textures, to get the hang of dealing with seams, patterns, bump maps, etc..

That's all I can think of right now! Hope it helps. And good luck :)