There are books galore about how to compliment your proteins.
eggs, beans, peanut butter, soy foods (there are many many many meat alternatives out there these days!) and protein powders should be able to do the trick.
be deliberate about replacing your protein and you should be fine. vegetarianism is something you should do only if you're prepared to take the steps necessary to keep your body healthy. do some research and good luck! i was veg for 2 years and i missed chicken so much that i went back :) i don't eat pork or beef now, but i do love poultry and fish!