Well, here's a suggestion, and I might be shot down for this....but if you are only 17, and still in high school, why don't you see if the high school has an athletic trainer..or approach a P.E. teacher/coach who you think you'd feel comfortable with, and ask them a few basic questions about how to use some of the equipment at the school? (supervised, of course). It's okay to ask one of those teachers - you might be surprised how impressed they would be with you for coming to them with some questions.
I know it won't be comprehensive, but a lot of them have done weight training in the past - and while they might not be able to give you all the specs about everything, you could learn enough of a foundation to proceed to a gym and feel like you could do something while learning and watching others.
Also, if you have a college or university close, see if they have an exercise science program there. Sometimes they'll offer like a summer strength training class and have personal trainers leading it....they also offer both short and longer packages at a discount that could help you along.
I've got a couple of really big BB buddies (one near my own age, one who is only 24) and they are really helpful whenever I want to ask a question, especially when I'm in the "big boy's" room at our university gym.
You should be really proud of yourself for wanting to take this step - and how careful and serious you are about approaching it. Good luck!