Just flash the Alt-F-0.1RC4 DNS-323.bin file using the box D-Link firmware upgrade page.
By default Alt-F will use what it finds on the disk *without* changing anything on them.
Be warned that a filesystem check will be started and might last for several hours; during that time you will not see your data. You can watch the fsck check evolution in the status page. *Don't* login until it finishes, as a first time wizard will automatically be started and the disk must be available at that time.
I also noticed that your RAID1 is in the degraded state (not providing redundancy) -- that might deploy a RAID resync, and that can take some 15 hours to accomplish -- but the data will be available meanwhile, although the box will be slower. You can also watch the resync evolution in the Status page.