edit: ah forgot: how do I play a low c on a guitar?
The 3rd fret on the A string should be your low C unless you're changing away from the standard tuning.

(The way to remember that is that each fret up is one half-tone higher. On the A string, playing it open is an A. Holding the first fret raises it up one half-tone to a Bb. The next fret is B and therefore the 3rd fret should be your C).
As for the sheet music, sadly I have no idea where to look. The sad truth is that almost all full arrangements of film music are locked up and not available to anyone except for performance reasons and even then the fees to access them are gigantic.

Though I assume you're looking for a guitar arrangement of the piece, right?