You're very welcome, I'm glad to hear you found it useful.

Do I really need the blender when I buy the juicer?

b_b's reply is very comprehensive in explaining the differences. The blender is definitely more useful. The reason why I recommend a juicer is because it's a lot easier to drink a glass of green juice extracted from let's say 2 pounds of greens than to eat 2 pounds of greens. Basically it's a way of drinking concentrated nutrition. It's true that a lot gets wasted, mainly fibre but if juicing is going to get you drinking more greens I say that's a good compromise. I emphasise the greens because they contain so much goodness, they're the best source of multi vitamins and minerals. And if you start juicing herbs, the concentrations of this goodness goes of the roof. Anyway, a juicer is not essential, it's just an enhancement to any diet.

How do I know when something goes wrong?

How does anyone know when something is wrong? Through symptoms. You can always do preventative tests. There are blood tests to check for certain mineral or vitamin deficiency. These tend to be quite expensive though. So the wise thing to do is what you're doing. Inform yourself on what takes to make a balanced diet, use tracking tools such as the links I shared before. Basically prevention is the best kind of cure, regardless of diet.

I've seen Earthlings. Came on it by accident - Hard to watch, but I think everybody in our civilization should see it.

Absolutely. Cowspiracy is a good second documentary more focused on the environment and less on animal rights. Basically any environmentalism approach that doesn't take into account the pollution caused by animal farming is doomed to fail.