All is NOT lost, as I can tell you from experience. And if you're ready to get fit (really ready) then you are in the right place.
I would spend some time reading the 100+ pounds to lose thread, lots of good info there, as well as some of my musings over the past two years.
FWIW, my wife was 302 (at 5'2") four weeks ago--now 13.5 pounds down just by making a few simple eating changes (and this with 0 exercise).
If there's anything we can do to help you, just say the word.
47 M 5'8"
May 4, 2010...... 440? lbs. (Start FitDay Size 60 Jeans)
June 19, 2010.... 393 lbs. (First Weigh-in)
June 19, 2011.... 229 lbs. (164 lbs. gone in one year :-)
Current Weight... 185 lbs. (Size 36 Jeans)
Next Goal 169 lbs. (07/04/12)
Ultimate Goal 165 lbs. (12/31/12)
The best exercises for weight loss are Fork Putdowns and Table Pushaways.