I have to ask...how is it you are expected to deliver--with no experience to speak of-- a scene complete with fully modeled, skinned, textured, rigged, animated characters, some special effects and then ultimately rendered in under three weeks?? I am assuming you don't have a day job, but even so, that would be a tight deadline for a team of seasoned pros. Seriously. It is possible for a noob to do it...but a more realistic deadline would be 12 months (for something half-way decent) if you are having to teach yourself everything.

I'm not trying to rain on your parade, but you cant even figure out how to model yet, let alone all of the other things that you will need to know. There is nothing wrong with being where you are at in your knowledge level...just don't expect to pull that off by yourself where you are now, man. Unless you are delusional or naive. ))

If you have to have something...buy some finished models at least and work from there.