use qtparted or gparted-- or even cfdisk (which is more powerful & dangerious-- but will 'make' things work when others fail).
reboot after each update of the partitians.
you will have the choice changing only one drive at time.
you will also (possibley) need to update your /etc/fstab file to reflect your updates.
no biggy... just come back here BEFORE you want to crush your sys