Bob,
I believe that restoration of any collectible is a mistake. Not just my opinion, but this is supported by collectible values in many categories. If the piece is so bad that it is worth only a fraction of what it might be otherwise, you may improve it's value, but it will never rise to the value of a piece in original condition. Of course, passing a restored piece as original would be unethical and could severely damage one's credibility, especially in such a thin market as the one that HLs trade in. If you have such a piece and wish to restore it for your own enjoyment, well, follow your heart. But if you are considering a purchase, caveat emptor -- let the buyer beware!
Happy New Year!
-Art