Please help! Hair perm problem!?

I have an appointment soon, to have my hair permed, but am now having second thoughts!! :( I have been told that it can cause loads of damage to the hair, it wont work because my hair is dyed black and i would look silly (lol). Please does anybody have any information about perms?!? Like are there different styles, and how they work?? My hair is long, about midway down my back, can you get like a wavy perm or something. Anything you know would be helpful, even if you just think I shouldnt get it done!! thankss x