I eat a lot of meat, usually for two meals each day. It's often chicken or fish, occasionally red meat. I was going to start introducing Meatless Mondays but then I figured why not go the whole hog (pardon the expression) and tried to do two full weeks meat-free.
I figured out prrreeeetty quickly that I'm very intolerant to most legumes, and I already know that my body doesn't react well to soy. Eggs, nuts, broccoli, quinoa, and spinach were all good alternatives I tried to incorporate into my diet, but I found it hard to make sure I was getting enough protein every day. I would have a protein shake for breakfast but didn't want to have more than one a day.
I found eating vegetarian was a lot cheaper than eating meat, though. A can of chickpeas was about $1.50, and that would give me two-to-three servings of whatever recipe I was making. The organic free-range chicken breast I usually buy costs about $5 for two servings.
I personally won't be going full-time veg, but I'm more aware of how eating meat can impact the planet. I've started eating kangaroo as a great red meat option, as it's got a relatively low carbon-footprint. You just have to get used to the idea of eating kangaroo, then you realise it's delicious.
I did make a delicious chickpea curry I can recommend, even though it made me bloated as hell (kind of worth it). Also The Happy Pear on YouTube have great vegan recipes, as does blogger Oh She Glows.
Difficulty: High, if you're used to eating a lot of meat. You gotta find new recipes, and make sure you're still getting enough protein and iron.