Lol Im doing this on my Rant too as I type.
ventones.com > Create Free Ringtones > Browse through your music files and find the song you want to make a ringtone > Use the slider and select a 30 second bit for the ringtone > Hit okay (or whatever it says..I forgot xD)
Thats it. If you dont have internet at the moment {{like me}} it has special directions. Oh, and when you sign up, it asks for the phone model. Hit Samsung in the filter, and then in the next column not listed, because the Rant isnt listed.
Not sure if you can record though.