You can download 3DS Max Educational version for a free trial from here http://usa.autodesk.com/adsk/servlet/pc/item?siteID=123112&id=14707612
Get your mum or dad to help you out with the forms, though.
You should be able to get a few months use out of it to start with. The best way to learn quickly is to follow along with some tutorials on You Tube - here are some simple ones to start with:
What the buttons do: (Super basic starter lesson)
Basic Model to start with - FISH!
Speed-video of modeling a Mario head: (Just to give you an idea of how the whole process works + inspiration to keep going!)
Making a character: (Part 1 - a lot more work!)
These are plenty to start with, but when looking for more, some key words to look up on You Tube are 'low-poly model', anything with 'tutorial' in it or words like 'simple' 'basic' or 'easy'. Always make sure you put in '3ds max' first, so you get tutorials for the right program.
Whe you get to the point where you want to start making your models move - look up tutorials on 'skin modifier' and 'biped'.
Since you want to make Zelda characters, try and collect some good front and side view pictures of them to use as references. As a beginner, you should be able to make characters like the N64 types fairly easily, once you get the hang of the controls.