You can do it! We all know it's hard (good grief, is it hard!!), but in the end, it is so worth it.
There are a couple of things you need to keep in mind about how you will be viewed by the others at a gym. The first is that the vast majority will not even notice you beyond a brief glance. They are there for their own effort, and need to stay focused on their own workout and can't spare much effort to take in the scenery. The second thing is that those that do notice you will be thinking 'yay for her - she's getting fit!', not 'holy cow, a fat woman'. Gyms have all different sizes attending, and the people there are almost certainly used to seeing people that are much fatter than you working out.
In my experience, most people at a gym or a class are friendly and encouraging, and are glad to see you trying to take control of your health.
You really should get a trainer to show you how to use the equipment. It is possible to injure yourself with poor posture or technique on many machines. You can ask for a training session during a slow period (ask - different gyms have different slow periods), if you want to keep the number of people around to a minimum. A trainer should also help you learn what is a realistic goal for you at first (you are not going to hop onto an elliptical for the first time, and go for 20 minutes). Most trainers are glad to see and help people like us. Their job is to help people get in shape, and when someone like us walks in and sticks with it, they are so happy that they were able to help. It validates what they do.
There is also one thing you need to do for *you* - change how you are thinking!
I too, let my weight be an excuse to not do something I wanted to do for a long time (in my case, I wanted to learn to belly dance). I was afraid that people would think I was silly looking, or ridiculous. I was afraid to try, and I let 10 years (!!!) pass before was able to change the way I thought. When I turned 40 last year, some switch flipped in my brain, and I realized it was foolish to let someone else's opinion matter more than mine about MY life. *So what* if they think I look silly. I'm not doing this to please them, I'm doing it to please myself. This is all about ME, not them. You need to start thinking it is all about YOU, not them. You are doing this for YOUR health and well being, not for them. So what if anyone thinks badly of you - you don't care what they think because you. are. not. doing. this. for. them!
BP