If you put the case out in the sun or trunk of your car and let it get really hot it will help kill the mildew/mold that is causing the smell. You can also wipe down the inside with a mild bleach solution. But the mold is in the glue under the lining so not always helpful.
I have found that this works better then just trying to cover it up with Febreeze or other deoderants.
Sounds like you got a good deal. Be careful it is very addicting.
Also, you can check the felt or cardboard oil absorber under the bottom and replace that if the machine itself smells.