Walking is a great way to start out. It is low impact, burns calories, increases fitness and cardiac health. Other suggestions are crunches and half push ups (with knees on the floor and ankles crossed) go to failure with them and try a few sets of each.
I believe you can build muscle not matter how big you are, it is just that you won't actually see the muscle until the excess weight comes off, but by the time it does you will probably have a 6 pack and big biceps under it all
You could get some dumbells and do some bicep and tricep exercises. The higher the muscle mass the more calories you will burn each day even when you aren't exercising.
I agree with you about the low carb thing, it is just not sustainable for most people, myself included. I love my carbs, they fill me up, give my body the energy it needs to work out and of course they taste good! You just have to choose the right ones. Most fruit and some veg such as corn, potato, sweet potato are all sources of good carbs. If you like your bread then I can highly recommend the wholegrain and seeds burgen bread. The slices are smaller but they really fill you up. It is high in protein, higher in fat than most breads but is 'good fat' and lowest in carb of all breads I think, also very high in fibre which helps to make you feel full. Just make sure you don't overdo the carbs at night. It is fine to have a serve of potato or corn (or even both) with your dinner, or some pasta, but portion size is the key.
Another good habit to get into is drinking warm water with fresh lemon (I use 1/4 lemon per cup). I have a cup most morning and nights as it makes you feel more full so you don't have a massive meal, it really curbs sweet cravings (you wouldn't think so but it does work) as well as gives your liver a cleanse.
A fantastic book that i'm in love with is 'Sly moves' by Sylvester Stallone, I think most men (and women) would be inspired by this. It is a really down to earth approach to weight loss, fitness and health. In it he talks a lot about foods and you can learn a lot about nutrition, he also gives loads of exercises and talks about his tough training regimes (for inspiration) about his famous movies Rocky's and Rambo's. If you search for it on ebay you will prob only pay $10 or so all up if you purchase internationally.