Moving onto RAID is actually retty straightforward, but you need to be comfortable with the following items and a spare disk is more or less required.
making a boot floppy OR getting REALLY good at getting LILO on the MBR of another disk.
shuffling partitions; I use
mount (empty partition, formatted) /mnt
find . -xdev | cpio -pm /mnt/
do the same for the /boot partition
get this new partition bootable and runnable as the LAST disk on the system (the first disks will be used for the RAID array)
configure and format the RAID array as per the howto
copy your filesystem to the RAID array as above.
read the Root RAID Howto!
Don't put anything else but the swap on the drives that use RAID. Multiple mount points alongside the RAID will hurt performance.
I use a lot of RAID-5 and the 'failed-disk' parameter works great as you can have your root filesystem on the first hard disk, mark it as failed in the array, build the array, copy stuff to the array, boot and run off said array (to confirm operation) and then repair the array (by adding the first drive back into the array).
brain hurts - gotta go.