Well, when you load the file, get the statistics on it. It's under analyze. Look for clipped samples and dc offset. If you have clipped samples, you'll need to run the clip restoration feature, which is under noise reduction. If you have dc offset, you'll want to fix that too. Use the normalize function, and click on the box that says "dc bias adjust." Keep it at 0%. Also, if the sond is abnormally loud to the point that the waveform appears cut off and overdriven, use the normalize feature to reduce the db level. -2db is usually pretty good.
Do these things first. If everything appears normal, just make sure the song isn't too loud that it will drive your speakers crazy. If you have probelms, and after fixing the easy stuff it still sounds bad, you'll probably need to run some filters, especially for bass distortion. Filters are basically trial and error- just mess around until something works.
I hope this helps. If you have any other questions, feel free to e-mail me at firstname.lastname@example.org. I'd be gald to help however I can.