As well as Audacity, WavePad is a good free program - but if you already have a wave editor, not sure you need another one - they all work in pretty much the same way in my experience. It might look daunting, but it's pretty simple - no substitute for having a go.

Use the program to open the track you want to edit, highlight the segment of the track you want to use as a ringtone (you might have to play bits of the track first so you can find the exact segment), then under the 'Edit' menu you should have an option called 'Copy to File'. Choose that, and you should be able to save the highlighted segment as a new file. That way you don't have to mess around with the original track any more than you need to.

Then open up your new file, and do any further editing you want. To delete bits of the track, just highlight that piece and then click the 'Delete' option under the Edit menu. When you are done, make sure that you save your final version as an mp3 - the program may not do this automatically.