All great advice here! I love how gentle people can be on this forum, and still throw the facepunches when necessary. :)
I just wanted to add that, perhaps for phase II, remember that you can start adding extra ingredients to the premade foods that you'll start by buying and transitioning too. Someone mentioned the frozen pizza option. We have a good grocery store one that's about 10$ for a huge pepperoni pizza. But remember that, when you're feeling ambitious, you can start adding your own extra toppings! Different cheeses, add some finely chopped spinach, whatever. Same with pasta sauce: buy a jar to mix with your pasta, and then start adding extra veggies or browning your own meat first. Buy a deli bean salad and put it over your own lettuce, or buy a rotisserie chicken and add leftover bits to a can of vegetable or bean soup.
I think thinking of this in terms of phases would be useful, and I agree with the poster who mentioned that your taste buds need to adjust too. So after a few months of just swapping grocery store/deli items for fast food items, push yourself to just try different flavours, and, as above, transition to "cooking" habits. Ie--don't worry about making things from scratch yet, but do get in the habit of doing a little bit of extra prep in your kitchen, the *routine* of cooking. Then, as others have said, maybe a few months later, you pick a couple of days a week (weekends) that you'll try a recipe or two from scratch just to see how it goes.
Recognize that what you're aiming for is (hopefully) something edible, but the main purpose is to notice how different foods are made, what the basic techniques are. For instance, just about all soups are made the same way: saute onions, garlic, other seasonings, other chopped vegetables. Add some water/stock/liquid (not milks/creams yet), boil until veggies are cooked. Taste to add salt, pepper, or whatever else, and then either eat, or add milk/creams with any cooked ingredients (like leftover bits of veg or meat), simmer until hot through and then eat. Or puree a little with a hand blender and then eat. If you practice this sort of routine, you'll find that some variations work better than others, and occaisionally you'll make something inedible. :) But that's ok! I find it helpful to remember at these times that sometimes it's ok for food to just be fuel, it doesn't *always* have to be the tastiest thing ever, lol. I just don't freeze those leftovers!
Anyway, if you practice soup, you're a hair away from stews, chilis, pasta sauces, etc. Just go slow, and soon you'll have a repertoire of *techiniques* that you can use for any ingredients you want to use. Good luck! (I'm a big fan of cookbooks from the library too. Jamie Oliver's Save with Jamie is a really good basic one, for instance)