first you must be able to compile tremulous from the svn
(and you need to know how to get the svn)
and you need to run trem in a test environment
(use the compiled qvm's and binary and a atcs.pk3 and data.1.1.0.pk3)
now after the compile open game/tremulous.h
it has lines like
#define key value
key's are very self descriptive change the ones you want
recompile test
next place to look is bg_misc.c
it has class ( not c++ classes

; aliens/humans/weapons/buildables ) definitions and values defined in tremulous.h is defined there