As far as I've been able to tell, BIS is only a gateway, pulling email from your inbox(es) and routing to your BB and does not keep copies of anything. The only thing 'extra' it will do is filter emails (you set up the filters).
The only firmware I know of is the various OSs that are floating around the forum.
As to your firmware question, you can load any vendors firmware
the latest version for the 8310 can be found here
follow the directions and you'll be fine.