Hi Jonnyman20, I'm new to Maya too but I can maybe help a little, in your screenshot your model isn't centered exactly in the x axis, meaning when you go to cut the model in half it'll cut more over to one side and mess up the whole mirroring back over process, when modeling it's best to keep the model at the origin, when in the front view you should always have a line of vertices going exactly up the y axis so when you mirror over the two parts meet together seamlessly. Hope that's pointed you in the right direction, and hopefully someone else will explain more if you need it.