As you have the b2.00uns loader, you can just upload the CI3.1 FTA file using either the NSD (nokia serial downloader) or the DVBEdit.
But you have to know something, that, there are two (2) different kinds of nokia 9600. one cannot goback to the old CI3.1, this is from my experience.
The one with the word "Mediamaster 9600" on the front door shall not goback to the old FTA software.
The other one with only "Mediamaster", without the 9600, is can easily flashed with any one, dvb2000 or ci3.1.
hope this will help
;)