Minimal backup + restore with DM (contacts, emails, bookmarks, etc, reinstall apps manually. I wouldn't even backup your settings). Save the backup to an .ipd file and restore after you upgrade your 9900 to the latest os version (recommend 7.1.0.402).
Upgrade the 9900 software first, the older 7.0 os and earlier 7.1 os versions have some issue that are fixed in 7.1.0.342 or 7.1.0.402.
-Connect the 9900 to the pc via usb, load desktop manager (some initial setup stuff for the 9900 and desktop manager will happen)
-With the 9900 selected in DM, select Device > Restore
-Select your 9000 backup file
-Select "Select device data and settings"
-Uncheck everything that isn't needed, then restore
Ah, thanks! Will I be automatically prompted to upgrade OS when I plug the new 9900 into DM? Are the latest versions (7.1.0.342 and 7.1.0.402) automatically available? I'm on ATT.
Nope, AT&T is lagging behind on the updates, so you have to download the 7.1.0.402 leak, then delete the vendor.xml file and install through apploader (there are guides on this in the leak forum I'm sure).
Salesperson shouldn't need to do anything, you just transfer your sim card.
Just to let you know, I found restoring the web browser history from Bold 9700 to 9900 caused a fatal error. So, I would just skip that one for sure and just go for the most important personal data. Also I would avoid the user settings as well since OS 7 is much newer than the OS running on your 9000.