Personal trainers are a great if you are unsure of what to do at a gym. Most new memberships will come with at least one session but be prepared for a hard sell as evidenced by a thread on this forum a few days ago. There is also a lot of information out there for free that you can find with some Google searches. Check out the fitness magazines at the local bookstore and visit their websites for free tips if you don't feel like spending $100 on a bunch of subscriptions.
Have you checked out the
WISH boards? There is a lot of good advice over there and some good weight loss challenges.
I schedule my gym time like I do work meetings so they aren't optional. What time of day will depend on your schedule but I bring my gym bag to work and go strait there when I am off. It is more convenient for me and there is less chance of getting home and deciding not to go out. I am always signed up for running events because they keep me motivated. Sometimes when you have a 2.5 hour training run staring at you that is much needed motivation.
As far as the weight loss goes diet is just as important as exercise. There are volumes of books filled with information and research so one post won't have it all but I believe that both cardio and resistance training are important. There is a misconception that cardio is the only way to lose weight but weight training in some ways is even better. Muscle consumes more calories just maintaining itself so for each pound of fat you replace with a pound of muscle your resting metabolic rate goes up. That is the amount of calories your body needs just to maintain itself. Resistance training also continues to burn calories longer after you are done with the workout. Your body has to rebuild those damaged muscle fibers. After weight training I recommend a protein shake or meal replacement as your body will need protein and good carbs and if you don't supply them you won't maximize your workout.
The best way to look at the diet is to not look at it as a diet at all. Look at it as a lifestyle change, they are more permanent. Remember that food is no more then fuel. It isn't a source of comfort or a way to replace something else in your life. It is fuel not a friend, this is an often repeated motto on the WISH boards. I try to eat as natural of food as possible. Evolutionarily our bodies are still cavemen and not designed to eat processed food full of chemistry experiments. I avoid sugar as much as I can (I don't even have any in the house) and avoid artificial sweeteners, even Splenda, like the plague.
The best advice I can give for the diet is to eat a healthy breakfast like eggs or low sugar oatmeal and eat many small meals throughout the day. It will keep you feeling fuller than 3 large meals and will keep your metabolism spiked. Eating a hand full of raw nuts and drinking a tall glass of water 15 minutes before a meal will make you feel fuller once you do eat. There is a delay between being full and you brain knowing you are so wait 15 minutes before going for seconds and eat slowly. I also don't have anything in the house like cookies or candy. If you have a food that you know is hard for you to avoid don't even buy it. If it isn't there you can't eat it.
Good luck, there is a lot more info out there both on the WISH boards here and on the Internet in general.