I don't claim to be the best at any of these book openings, but I've played the sicilian for a long time (not reflected by my rating, I hang my queen in 80% of my games it seems).
I feel the way I learned it wasn't very theory-heavy at first, and the theory that I ended up learning I picked up from ingame play. So the basics are that the mainline sicilian starts 1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3. At this point there are a few options for black and I would say start out with the dragon 5... g6 in preparation to fianchetto your bishop and castle kingside. Then just play. Focus on your opponent's queenside and controlling, but not occupying the center.
Once you play that a bunch you'll find that it has some big strengths and weaknesses.To exploit its weaknesses though, your opponent has to know quite a bit of theory. Once you want to delve into theory try 5... a6 instead of 5... g6.

). What might I run into on the way as far as mainline deviations? Anything major?
Short version: I want to learn the Scicilian without plummeting my rating.
20 years ago, when I started playing chess in earnest, the Scicilian and Ruy Lopez did not appeal to me either as white or black so I got into the Queen's Gambit, Indian Defenses, and the Pirc to avoud open games.
Now I have gotten back into chess and regret limiting myself so much and want to start looking at the Scicilian for starters. Can folks suggest a gentle way I can jump into all the theory out there? I am quite comfortable with the Pirc, so any Scicilian variation with g6 is likely to go easier for me.
Please no one lecture me on not needing to learn openings unless you are a master. Not to be overly aggressive, but thats crap, openings having internal logic and pitfalls that are worth learning.
Thanks,
Dan