There's a lot of great info here, laur, so check out the stickies and get excited about changing your life! I'm 24 and over 300, but in just the few weeks since I changed my habits and started losing weight I'm having tons more energy and fun with my two-year-old nephew.
You can probably get a lot of exercise just playing with him and chasing him around the local parks.
And I know you feel it's a long way, but I think having mid-term goals is the most important part of losing weight (everyone has daily and long-term goals). But it's the 1-2 month out goals that keep me focused and help build momentum. So get on the right track and set that goal for 200 and get some momentum!