ok, if you want to expand the drve, do you have anywhere else to put the partition? you can only expand the partition if you have free space one side of the partition on the drive. if you do then you should ba ok using resize2fs to sort that out, back anythign important up first tho.
you can only add an extra device to the tree by making it it's own particular branch, e.g /var/mail. you can merge two partitions together but it's pretty nasty, and complicated. so make your new partition (cfdisk, fdisk, diskdruid, diskdrake), and decide what you want to put in it, the use 'dd' to copy that branch onto the new partition, adn then change the mountpoints in /ets/fstab. all there is to it really