Hi erica, welcome to the forums.
DISCLAIMER: I have the uncanny abilty to rabbit on ad nauseum. I've tried to keep this post helpful, and believe it or not I've even tried to keep it brief (be thankful for that, I could have written a novel in reply to what you're looking for). Hopefully I've succeeded on the helpful front.
There's a lot of different good exercise programs out there. I could throw out some suggestions off the bat, but since I don't know what it is you want to get out of your training, it's hard to say. But for almost every conceivable goal, a good balance of strength and conditioning should be your focus in the gym.
I don't mean to come off as sexist here (great welcome that'd be!), but very often women in the gym will either avoid strength training altogether, or will tamper with their strength training (either by making it cardio with light versions of common strength training exercises, by not pushing for progress in the strength exercises they do, or by choosing exercises that they think will "tone" them instead of making them "bulky" - such a differentiation in exercise selection does not exist). Of the above examples of ways women often tamper with their strength training, the first is forgivable, because it is appropriate conditioning. But the other two examples are just a waste of time. Proper strength training is, however, almost a requirement to get anywhere for any given fitness goal. And remember, an increase in strength does not necessarily result in an increase in muscle mass (although for most women this would be a much better outcome than they often think it would) since muscle mass is just one component of strength.
Now, for your program, whatever your goal is, there's more than one way to cook a potato. So long as the majority of resistance training is compound movements and the whole body is focused on, your conditioning causes you to breathe heavy and sweat without hurting yourself, and you do strength and conditioning in that order, there are countless "right" ways to train.
So long as your actual strength training involves doing most exercises for 5-15 reps per set most of the time (unless you're doing Olympic lifts, which should be 1-5 reps most of the time) and you seek to either get more reps at the same weight or more weight for the same reps as often as possible, while making good form a #1 priority, you should be on the right track.
For cardio/conditioning, you can do marathon style training, but it's not the only way to achieve good conditioning. My conditioning (other than walking places) is usually over with in 4 minutes flat, because when you do it the way I do it, you don't need more than 4 min. That's probably hard to believe, but it's a proven method. Of course that's 4min after doing strength training for...well, longer than 4min
Interestingly, if I'm not mistaken studies have shown that for health benefits, all you need is 30min of moderate intensity activity 5 days per week. Less frequency and less duration yeilds less results, but a greater duration doesn't yeild significantly greater results, while a greater intensity does.
As I said before, have a look inthe weight training stickies.
You might also want to look in the running and cycling section, and the subsection on HIIT. That'll give you the principles you'll need to train effectively.
For motivation, I can't be there acting as your personal cheer squad. But if you do what I've said, which is to focus on progression as often as possible, then seeing your performance improve every session should give you all the motivation you'll need, for a while at least. As you get mentally exhausted from a program or chronically bored of it, look into other programs that focus on similar goals. Try to stick with a few central exercises long term (I highly recommend deep squats, deadlifts, bench press or dips, overhead press, pull ups or lat pull downs, and some form of row), but every now and again, learn different variations of the same exercise, and learn different assistance exercises (assistance exercises are anything other than your main exercises that serve to improve performance on the central exercises, that prevent/correct muscle imbalances and injuries, or that bring up muscles that need more direct work). Trying something new is usually fun and interesting, and can help keep you excited about training.
