Sorry - I never answered the bulk of your questions.

I need to be quiet while I meditate, but I don't need to be in a quiet place. Some of my best meditative sessions have been on an airplane. I do not chant or pray or anything like that - I would find that to be extremely distracting from the purpose of meditating. I do not have a particular posture, but I usually prefer to be sitting or lying down - I would have a hard time standing. At the meditation center I go to, 40 minutes of it is sitting, but we also have 20 minutes of walking meditation. I can do that easily now, but it was hard at first. I doubt I could do walking meditation while walking down the street, but in a controlled environment, it's not incredibly difficult. I don't use CDs but I do think that guided meditation would be much easier for those starting out than unguided, although mine is usually unguided. Occasionally one of my yoga classes will end with some guided meditation and I find that to be helpful, but at the same time, if you're really good at meditation then it wouldn't matter.

Benefits in my life are that I am able to quickly reduce anxiety (especially when flying and scuba diving). I am 100% confident that meditation practice will make my childbirth experience a lot easier. I make decisions more clearly after I've refocused and grounded myself with meditation, and I feel more centered and calm about things that I previously felt as though I "had" to control.

Hope that helps,
LMo