Y'know, I was about your age when I first started experimenting with 3D modelling. I strongly suggest downloading ALL of the Oinkerwinkle tools, Magos Model Editor, and the War3 MPQ Viewer. That aside, when you DO start experimenting, use the Bandit, Faceless One and male Villager models. They have the simplest meshes, and trust me, when you're using the vertex modifier for the first time, it can get REALLY disorienting.
Once you get used to the more basic model edits, I want you to look at my Shadeweaver model in Magos. It contains tons of the things I've learned through ALL my time working with Warcraft models, and it could prove useful to you. Good luck with your model edits; hopefully one day you'll be at a level like mine, giving advice to another new modeller.