moving to RAID..

Alright so I have a few questions about the nforce4 raid and just raid in general.
Background info: I currently have Gentoo installed and working the way I like it. I have 2 raptors and my partition scheme for the Gentoo install is:
sdb1 /boot
sdb2 /swap
sdb3 /

So for the questions, I would like to move this install over to a RAID0 across the raptors. What would you suggest as the best way to do so without losing/killing this install and having to start over? Also, is it possible to raid only a partition rather than an entire drive? For example to raid only the / partition? Or to Raid0 / and Raid1 /boot as mentioned in this thread http://forums.gentoo.org/viewtopic-t-400021-highlight-nforce4+raid.html ? The last I heard, GRUB wouldn't work on a raided drive. Does this still apply or how do you get around this?

I found this program called dmraid here http://people.redhat.com/~heinzm/sw/dmraid/ has anyone used this before? Will it migrate the current install over to the raid and setup the software raid? I know there was a program that came with my old computer in windows that allowed me to pick the disks, setup the raid, and then it would do that and migrate the OS install to the array. This worked even when using the drive the OS was installed on already. Does this make sense and is it possible somehow in linux? Thanks in advance.

there are two ways you could do raid, using the onboard nforce, or using the built in linux method. If you use the linux method, you wont be able to have windows access any of the raid volumes. You can have your boot partition on one drive, this will boot the kernel well, but whether or not you can mount the raid device (/dev/md0) as root, i dunno.
If you use the nforce, your two harddrives will be linked together to form one large virtual volume, you wont be able to have any partitions on just a single drive, you may be able to boot linux off of it, I dont have much experience booting linux off of raid volumes. You will have to make sure that the kernel supports the nvidia raid (are you sure its not a VIA or FastTrack chipset?) in order to see that virtual volume and mount the partitions it contains.

There is really no good way to migrate to a raid 0 setup by merging data into it. You could try copying the data over to a different area, setting up the raid, then copying it back.