Thank you Borromini for your reply.
When you already know where the information is then it is easy. Believe me, I have done several google searches and have not found much information. I already saw kirkwood downloads from OpenWrt download area, but not how to install those in a SheevaPlug.
The linked instructions explain how to boot from tftp server, but not how to install in into NAND or a USB device which is what I would prefer. If you already have done it, could you please write a small installation instructions post.
Than you for your information. It is a good start point.