What do you do with a coin covered with fingerprints?

When I first started collecting coins about 6 years ago I bought some $50 gold Anerican Eagles. Several of them have a thumbprint on them and one is darker than the others, less glossy and is covered with fingerprints. Should I get these slabbed and what do I have to disclose about the fingerprints when I go to sell them at auction? Is there a proper way to remove the fingerprints? I've always read that you never clean a coin. Is that true?