You no longer have to do the ssh to gain root there is a simpler way by using the gainroot.deb but since you are half way there I will give you the last push... when they say ssh they mean from your pc to the N800... If you do it from the xterm itself drop bear does not use ssh command it uses its own dropbear commands like dropbear-ssh or something like that... I would install openSSH if I was you...