The challenge of mountaineering is different that other endeavors. I'm planning on climbing Mt. Rainier in 2016. I know it's a long way off but that's when a buddy of mine graduates from grad school. So here's what I've used to start prepareing. This is the guide
Mount Rainier: A Climbing Guide (A Climbing Guide) 2nd Edition. Also check out summitpost.org, there you will find a lot of resources to help with the planning. My friends climbed it before and says that it is doable but training is key. By training he means, cardio, strength and then time at elevation. Before he did it the group summited The Grand Teton, car-to-car, in a day. He said it was long and grueling but paid dividends on Rainier. That said I don't think you should sweat too much.
I agree with you Mt. Rainier, for as daunting as it is, a major route to the top is highly accessible to a lot of people. This year was one of the mountains worst in terms of deaths though. You need to be up to snuff on snow travel and conditions. I've always enjoyed mountaineering, whether it has been peak bagging or true moutaineering. There is something about the freedom of the hills that is unparalleled with other adventures (e.g. backpacking, canyoneering, rafting, etc.) My first love is backpacking. I do my fair share of canyoneering. I also do quite a bit of rafting (thanks to my wife

). I've had many mountains on my radar for a long time, but I never thought about doing Mt. Rainier until my wife and I stopped there coming home from North Cascades NP. Since then a photo of the mountain has been hanging on my wall to remind me of its beauty and keep me planning the adventure of a summit attempt.
I feel like I'm sort of rambling now, sorry. I say you do it. You've already consented the fact that you might need more preparation by trying to figure out what you need to know. Therefore, I would think that you're not going to jump into anything that you don't feel confident you have the skills to do. So I say again: Plan, prepare and prevail!
Salud!