If you really are obese and don't know much about nutrition, I think the V-Diet is a great starting point. As for the protein shake, I only have protein shakes when I can't get enough protein from a whole source, or before bed, when having a proper meal would make it tough to go to sleep.
So, for example, if I'm having oats for breakfast, I have a breakfast shake to go with that, because there's no way in hell I can get enough protein from milk and oats alone.
In your case, I would add egg whites to breakfast (1 whole egg, 3 egg white and 10g olive oil plus some tomatoes and bell peppers make a mean-ass, healthy, low-carb breakfast). For the snacks, I'd look into adding lean, low-carb coldcuts first, and if that's too expensive or inconvenient, turn to protein powders. Before you go to bed, have some meat or the cottage cheese.
Whey is cool because it's fast absorbing, but it's not very versatile or handy for dieting because it doesn't stay in your body for long, and doesn't fill you up as well as egg protein + fats, or casein. If the V-Diet is out of your range financially, then look to alternative sources of slow-digesting proteins. This brings us back to cottage cheese, lean cuts of meat, eggs (less so).
As a final note, here's how I'd rearrange your present diet and where I would add the protein to make optimal use of your resources:
Peanut butter, NO toast
1/2 Sweet potato
1/4cup of almonds
1 can tuna
(I would add some extra virgin olive oil)
1/2cup edamame => this really ain't cutting it, I'm afraid. I would not be eating the edamame at all, or I'd eat it as a side. Change this to a coldcut, add some tomatoes or whatever else you need to make it more palatable.
6 oz chicken or ground turkey
150-200g cottage cheese