50 dollars for the dock is fantastic. Do it.
Dell has the basic drivers and system utilities online.
I don't think I kept much else, but that is strictly me.
Make a backup of the system as it arrived, but after you've updated windows and drivers. Then back up your backup.
That lets you remove stuff with a safety net.
I contacted Dell via email and politely requested OS and driver discs for my Duo, (making sure I told them I understood there might be a fee involved) and was pleasantly surprised to be told that the discs were in the mail!
I just checked my email again -no less than 5 discs heading out here. wow!
(PROPS TO DELL, SERIOUSLY)
As far as accessories go, a USB DVD drive can be extremely useful, but if that isn't a pressing need, consider either picking one up from a less costly retailer or, consider re-purposing and existing drive with an inexpensive USB enclosure.
I had an extra laptop DVD burner drive that has done excellent service, mostly installing operating systems.
I have a slip-cover type case, but no other real plans for accessories.