JUst so people know if they visit with this question:
Its an "Install" via twrp and you can keep it in the zip format to do this. Its essential that a good wipe is done first though otherwise it retains chunks of nabis-desktop and then tries re-downloading the missing bits.
So after making a full backup just in case.
So go into TWRP with the zip file on your sd card. Do a really good wipe in the advanced wipe settings (dont wipe external sd card). Use twrps "install" to browse to the zip and install it. Then reboot. THats what worked for me.
You still get the awful blue nabi lockscreen, not sure yet how to remove that.