I hope you don't take this as me being rude, but chances are that people don't know the answer.

About updating the firmware, I did the same thing, set up the 800 to my liking after doing the dual boot, only to find that there was an update that I didn't know about....rats!

So I updated my firmware after making a backup. Redid the last few steps of the boot from mmc, and everything was in tact. The firmware in the about screen was updated, all my apps were still there, settings, home screen, everything. Again, I don't know if in your case you'd be able to keep your phone book etc.