ROM Hack Harvest Moon DS/DS Cute Sprite Hacking

[DerpyGz]

Hey, I am trying to hack a Harvest Moon game, mainly to change the sprites, but if I am able to edit anymore I will. I am able to get into the actual game files by using Nitro Explorer but am having a bit of trouble getting the right tools actually find, open or edit sprites. I have done a Fairy Tail hack on Pokemon Diamond and Pearl, so I have a little bit of experience in hacking, but I am oblivious so please try and explain it rather simply. If you want to know what I want to do with the hack, I would like to make different characters and range it from creating anime characters (mainly Fairy Tail) to just making the bachelors more attractive XD Thanks to anybody who can help and sorry if I ask a couple of questions.