This is a guide how to change the SMS ringtones on your 1.1.1 iPhone on a Mac Please note that I tried this with no longer than 5 seconds long files. If somebody tries it with a longer one - please post here with the result.
I'm using Switch to convert mp3 to aiff (here's the link - http://www.nch.com.au/components/switchmac.zip ).
Step 1. Choose the file you want and convert it with Switch to .aiff.
Step 2. Use Fugu to ssh into the iPhone. Go to /System/Library/Audio/UISounds.
Step 3. Find the files sms-received$.caf, where $ stands for 1, 2, 3 til 6 and choose one of them. In my case I am using sms-received6.caf, because I don't like the Electronic ringtone anyway Make a back-up of this file on your computer.
Step 4. Now you have to rename the file that you created in step 1 to the same name as the file you have chosen in step 3 - in my case sms-received6.caf (Be sure you change the file extension as well and not make it sms-received6.caf.aiff).
Step 5. Using again Fugu put the newly renamed file into the same dir (/System/Library/Audio/UISounds) and restart the iPhone.
Step 6. Now in Settings -> Sounds change the New Text Message sound to the one you just put in (in my case I have to pick the Electronic one) and you are good to go.
And here is which file corresponds to which name:
sms-received1.caf -> Tri-tone
sms-received2.caf -> Chime
sms-received3.caf -> Glass
sms-received4.caf -> Horn
sms-received5.caf -> Bell
sms-received6.caf -> Electronic