This should take care of not being able to modify /etc/fstab:
mount -o remount,rw /
As for the RAID0 recovery, I guess it really depends on how you deleted it and what details you have about its construction, but I suspect, while I've never attempted this myself, there is a facility within mdadm to allow you to lay down the information again if you have all the specifics.
Hope this helps.
If all you did was delete the partition, it may be as simple as recreating the partition with the same start and end cylinder and setting the partition type to: fd Linux raid auto