I think it's best to first find types of exercise that you enjoy doing so that you'll stick with it on a regular basis. Then just modify the exercises to meet your needs. For example, I took a yoga class called, 'Yoga for the Buddah Body' and it was geared for obese bodies. Basically we learned to use the straps & blocks to accommodate our belly fat, etc. So actually anyone could do it on their own without taking a class by just modifying the regular poses to accommodate your body & using the blocks & straps. I use a large ball to do my abs on b/c I can't do the exercises laying down flat. I bought a rebounder to do aerobics since I can't handle impact movements on the floor at my size.
Basically, my advice is to do the exercise you enjoy the most then just do what you can to modify the exercise to be tailored to your own body. BTW, after a while it's amazing to watch how much more you can do in such a short time and gives a boost to your motivation the first time you're able to do the exercises without having to modify them.
Congrats on your choice to exercise! Also, if you want some motivation to walk more and give yourself some accountability, Almeeker started a pedometer challenge here. I'm just starting it, but I think they list their weekly steps at the end of every week.
"Most folks are about as happy as
they make up their minds to be."
- Abraham Lincoln