I'm kinda confused as to why you would need anybody to do art or music or...well anything besides programing. I thought that was one of the good parts about blatantly riping off someone else's game, all the music, sound effects, animation ext. are already done.
as far as making you own bosses, just steal them like you do with every thing else and just add some stuff
its DILDO MAN....Bu dum bump.. bu dum bump.. bu da da da da DA
See its easy.