It is easy to get all the nutrition you need from a vegetarian diet - it's not tricky at all. It's a myth that you need meat for protein etc. Quinoa is a great grain source of complete protein and it's delicious eaten like a rice as a side or you can even make dessert from it.
You can also use meat substitutes, although a lot of them are highly processed. I suggests making your own. There are many recipe blogs and sites all over for vegetarian recipes. One of our favorites that even our meat eating friends enjoy are black bean burgers. You can soak TVP (textured vegetable protein) and use this in place of ground beef as well. I have gluten/wheat issues so I can no longer do that unfortunately, but when I first went Vegetarian years ago I loved using TVP to make lasagna, burgers, casseroles etc.
The bulk of nutrients in our diets are plant based - you're more apt to get more of what you need by simply eating fruits and vegetables. :) good luck.