Assorted WP-34S beginner questions

[sa-penguin]

Inspired by some Uni homework on numerical methods (Newton, Householder, Halley, Taylor series etc.) I went looking for the 34S code for trig and square root functions. However...
With all the subdirectories and code - I got lost.

Is there a "Code for Dummies" for the 34S code?
That "Command Alias" PDF is nice, but: given an instruction, how do I find the source code for that instruction? I'm looking for the trig functions, but really there should be a lookup for every function.
A search of the trunk for "COS" shows it in commands.c xeq.h complex.c but I'm blessed if I can find where cosines are actually evaluated.
What am I missing?