Nope, you do it the same way. Apparently there is a rumor and evidence in iOS 5 betas that you'l be able to add custom text tones and purchase them like you can with Ringtones.
Or you can use biteSMS, which is absolutely painless and can use any ring already on your phone, assigned to the contact of your choice. No renaming, no SSH required. I believe ToneFx also allows for easy changing of text tones, but I haven't tried it and can't say for sure.
hm... you are in the iphone hacks section. Of cuz you get answer that needs jailbreaking. If you don't wish to jailbreak and get custom ringtones then post it in the iphone section!