what do you mean for the first part? you mean that on boot you always need to specifially choose that option?
if so and assuming you're using lilo, just change the /etc/lilo.conf default= line, or rather go further and edit the conf file more widely. then run "lilo".
as for then second... you should just want
hdparm -d0 /dev/hdXY
i think. check the man page for hdparm first.