Lots of great advice! I would add the importance of learning to do the exercises correctly, and slowly. Know exactly which muscles each exercise is targeting, and remember to breath. It will make a difference in your form and execution. It is unlikely you will build huge muscle mass, however, you will loose the tone you have gained quickly if you are not consistent in your workouts. It is amazing how much progress you lose when you take a few weeks off. Charting out your workouts is helpful, keeping track of weights and reps for each exercise.
For cardio, find something you enjoy doing. Aside from running, there is always skipping, jump rope, stairs, swimming…mix it up so you don't get bored. Working out with a friend is a great idea. Much harder to wimp out if someone is waiting for you to show up......and it can make it more enjoyable for you.
Anyway, the amount most of us are on the computer or watching TV, finding some dedicated time to work out is usually not impossible. Just a matter of priorities. You mentioned you have free time, so thats great. Think of it as a great investment for your mind and body.
Exercise can help insomnia, but don’t work out too close to bedtime. And you know, Grandma was right…warm milk (warm, not hot) will help you sleep.
Good luck!