i) First, I don't have a Fortran compiler yet, hence, I think I won't be
able to compile the numerical package, is it right?
no it is not needed
to compile under clisp:
if the command to invoke clisp is 'clisp'
cd src
make clisp-compile CLISP=clisp
and the xmaxima should be invoked with
export MAXIMA_DIRECTORY=/home/wheretofind/maxima-5.6
xmaxima -lisp clisp