This sounds like an excellent and very ambitious project. Since it is a high school project I'd suggest that you don't get too complicated. As I thing Richard pointed out it can be very complicated but treat the project as a pilot - keep it simple and just remember to point out the limitations when you write the report :) Then like any good researcher you can ask for more funding for future reseach :)
> iii)Is there some easily available (preferably free) software that > will let me do all this analysis (brownie points for fitting > probability distributions and graphing)? It would be a nightmare to do > this by hand since we usually work with less than 50 data points > instead of several hundred.
Perhaps the Royal Royce of free statistical packages is R http://www.r-project.org/. However it is not all that user-friendly and it might take longer to learn than is worth it for one project.
There is plenty of good documentation on the site that can help and there is a very good R-help mailing list where you can ask questions
Otherwise here are some sites for some dedictated statistiscs/ graphing packages (Free or shareware in most or all cases). I have not checked the links in a few months though.