I'm not a fitness professional, so I can't really give you much particular advice: you do need to work with weights as well as doing cardio. I personally like the elliptical runners more than the treadmills, but I think it's mostly a matter of personal preference. I think ideally you should be doing an hour of cardio 5 days a week (this might be something you work up to) and lifting weights 3 days a week.
What I do want to say is that you need to be more assertive with the staff at your Y and get them to actually help you, and properly. They might be busy, but introducing people to the equipment and to a workout routine is their job. I suggest making an appointment to work with a personal trainer--my Y offers this as a free service when you join up. If yours doesn't, you can still pester them until someone gives you a half hour of their time and shows you how to lift weights and use the machines properly. We don't want you to get discouraged and give up exercising, and if you're wandering aimlessly around the gym, unsure what to do, you're going to get discouraged, or you are going to get hurt. Don't be afraid to be assertive!!!