Congratulations on your new ride (Great choice and it looks like it was kept in amazing shape). Where in SD are you? Make sure you check out the So Cal section of this forum for upcoming drives. We actually have one coming up for 3/26 (http://www.nsxprime.com/forums/showthread.php?t=146538).
It is not possible for you to shift into Reverse when you are wanting to get 6th gear b/c the computer has an auto-lock to prevent this from happening when the car is driving forward.
Enjoy and hope to meet you at some of the upcoming drives!