If you will still be eating fish you will not be a vegetarian, you will be a pescetarian. Plenty of protien and omega 3 available from plant sources if you are interested, wallnuts are particularly good for omega 3, as is flax/lin seed. In reallity proteins are not that important either, its the complete range of amino acids that the body breaks protein down to that the body needs. Soya, pulses, nuts and the like are great for healthy oils and proteins.
To answer the question, not a new year's resolution but just a date chosen to start making a change. Right now I'm a vegetarian but over the course of the next 3 months I will be in a learning process with the goal of becoming a virtual vegan. I don't feel a moral compulsion to make the change but I've done a fair bit of research and believe a whole food vegan diet to be healthy to the extent that I believe it will relieve some of my health issues. In practice this means all food prepaired by me at home will be vegan but eating out will be whatever I choose, as long as it's not meat or fish, if visiting others I will, again, eat whatever veggie food I am given.