The first thing you need to know is that there are as many workout routines and philosophies as there are people working out, so everybody's going to have a different opinion.
The second thing you need to know is that getting heavy thighs and triceps should be very low on your list of concerns. It's just not likely, and if it ever happens then you've got a better problem to deal with than being fat.
If you're really serious about this, then I'm not really going to be able to cover everything you need to know in this answer, but I would recommend that you grab the following book to learn the fundamentals of weight training:
Third, you're not going to reach your goal without a combination of exercise and diet. However, what I want to stress is please do not go on a crazy crash diet. The crazier and more difficult your diet, the higher the likelihood that you're going to fail.
Start slow. Take a month and pick one of the most unhealthy things that you eat on a regular basis and then stop eating it. Focus on sweets (esp soft drinks or fruit juice) and really high calorie things. That's it... Don't change anything else.
Then, if you're successful in the next few months pick a few more things and do those. For everything else, don't stress too much. Just make little deals with yourself. If you really want the bacon cheeseburger, then compromise on just a regular burger. Or if you have a really unhealthy lunch, try to eat something healthy for dinner.
One thing people don't realize is that dieting is really permanent behavior change. If you stop drinking soft drinks, then after six months or a year you'll stop wanting soft drinks, and after more than a year you'll probably think they taste gross.
Just don't overdo it.
Now, on to the strength training.
You'll read about this in the book, but you'll probably want to target your workouts to 12 rep sets for a good combination of muscle growth and endurance. You do want muscle growth, because that's what burns calories. After six months or so, I would bump up the reps to 15 or maybe a tad more to focus more on endurance than muscle growth. At that point you could also look at circuit training to get more cardio involved.
In the book there is a very simple workout routine. Just keep it simple. Focus on big exercises and not isolations. Along the same vein, it's a myth that you can isolate problem areas (like fat thighs) with thigh specific exercises. The fat's going to come off where it wants to, and the large whole body exercises are going to be more effective at that.
Make up your mind that you're going to be in it for the long haul. The first couple of months are going to be horrible. You will be tired, sore, and you will have less energy. All of this changes after about two or three months, and you'll start to have more energy and you will feel stronger.
Also, every week try to increase your weight by a small amount on your exercises. This is where the motivation comes in. When you come back in two months and you're now lifting 30% more than you did when you started, that's motivating.
Always warm up with a mile or so on the cardio machine or elliptical or you'll hurt yourself
Pay lots of attention to the proper way to do exercises or you'll end up with tendinitis because of disproportionate joint loading and other things. You do not want this.