lsmod doesn't need any switches, i don't think it even has any. it should list(ls) all the modules(mod) running.
as for why it's giving you the usage is beyond me. could be due to insufficient privileges or something, try running it root or su(run 'su' and enter admin password when promted).
try building the fglrx module yourself.
su or login as root and type the following into a terminal:
if it complains about ./make then precede it with perl eg. 'perl ./make.sh' and do the same for the install script.
then restart linux.
as for the monitor frequencies, you cant go wrong with the std vga 1024*768 option, H34-60 V50-100(i think) unless you're using some REALLY old monochrome