i think you should finish it, i really think that if you try and finished modeles yeah starting out, you learn a lot more than just say doin a fender on 10 cars. even if its not the best modeling, i still think you get so much more out of finishing projects
as for renders, there a couple of choices
vray, you can pick up the demo here
Chaos Group home page - V-Ray, Aura and more
Mental ray, that comes with max 8
Maxwell, demo can be found here
Maxwell Render ™ : The Light Simulator. Render engine. Multilight ™. Materials. Photorealistic...
bascily they all do the same thing, (like most 3d programs) just have different way of gettting there, i would recomend metal ray for now, its free and should be already on your computer.