For any painting, I just use Photoshop Elements. For doing sketches or line art, I usually will bounce back and forth between Paint Tool Sai and Photoshop depending on what I'm doing. For straight up vectoring, I use Paint Tool Sai. If I'm doing something with more of a "manga" or comic feel I'll use manga studio. Here's an example of that;
As far as tablets go, I use a Wacom Bamboo CTH-470. It's kind of small but I love it since I'm more of a wrist guy anyway with my brush strokes. And no, no formal training.
These books, however, are goddamn fantastic and I recommend ANYONE read them no matter what their skill level is;
http://alexhays.com/loomis/