that is a FAQ: Alt-F will not change your disks in any way unless you tell it to do so. It will happily use what it founds (including RAID)
Even the default option on the first login wizard is "don't touch my disks on any way".
That said, you will have to recreate share definitions, users, etc. Settings will not be read and used from D-Link fw.
*Always* read the popups, as they will warn you of possible data loss. And don't use IE!