Cardio - okay to do every day. You mainly want to rest to give your muscles and joints a break. Cardiovascular workouts are for your heart, and keeping your heart active is good (but don't do it at the expense of your structural body).
Cardio + Weight Training: Yup! I've read that doing cardio AFTER 15 mins of weight training or so helps dramatically increase your HGH production as opposed to vice versa. HGH is important for keeping yourself healthy and looking young.
How to start weight training:
I could write quite a bit on this, but I'll keep it to some simple tips:
#1 - Ask people to show you how to use machines : Form is very important. You don't need to get personal training, necessarily, but ask one of the trainers around the gym to help you out a little bit. If not, ask someone who knows what they're doing. They should be glad to help you out.
#2 - Muscles grow at rest, not during exercise : Rest muscle groups after you work them out. Your body rebuilds muscles as a response to the load you put on them. When you work them out, you're really damaging them somewhat so your body can rebuild them stronger. Alternate muscle groups you work each day, and reserve 2-3 days each week for full rest.
#3 - Nutrition : Proper nutrition is the backbone of healthy living. You are, literally, what you eat - so fill yourself with the best and you'll be the best. Eat well, get enough energy (carbs, protein, fat) for your workouts. You can also look into supplementation, depending on how dedicated you are.
For weightlifting, you're running primarily on highly bioavailable energy nutrients (carbs) so you'll want to make sure you get some of these at least an hour or two before your workout. If your workout is particularly strenuous, during.
#4 - Start slow : As you get more into it, you'll want to test the limits of you strength. Start with lighter weights until you're sure you're targeting the right muscle groups. With each exercise you should know which muscles you're working (this is often printed on or near a particular machine). You should be able to feel the burn primarily in those muscles -- if you're not feeling it, or you're feeling it somewhere else, stop and critique your form, or get help (See #1).
