you should make up your mind for alteast 24 to 28 hours to reach Hunza with necessary stops..
you can go via either Naran - Chillas route by crossing babusar pass, or through KKH.. both have their beauties and attractions but to cross babusar pass u would require 4x4 depending upon condition this year as i read in news last year that during flood public transporters uses this route while coming from Gilgit to Mansehra.. which was little strange to me..
you can spend night in either Chillas or Gilgit.. but Chillas may be little hot.. from Gilgit it is around 2.30 to 3 hours drive..
for better road guidance.. i suggest u do some search to get some road Maps from net.. or i think u can also try to buy from some book shop..