I personally avoid replacing labels if at all possible. But I understand if you do. just as long as the label has somewhere marked it is a reproduction label. If i found a really rare game but the label was ripped in half and it was too cheap to pass on, I would most likely look at a replacement label myself til I can find a better original label. But if it was faded, light tears, nicks and scratches no, I'd rather it have some wear then a perfect reproduction fake. I've turned down buying obscure games due to the label being damaged. The only thing I don't like about them is if I walked into a game store and bought a game thinking it had a mint label then find out it had a replacement label I would not be happy. To me a replacement label is the same as buying a game with a heavy damaged or missing label. If I replaced a label then wanted to sell it I'd list it as "REPLACED LABEL" and discount it heavy due to this. There's many collectors who would rather buy a missing label over a replaced one.
The other problem about replaced labels is that it makes people suspicious the game could be a reproduction too. If your buying a game for your own personal collection and just want it to look nice, then okay buy a new label, (make sure it says "reproduction" some where easy to see) but if your buying a game to sell/trade then it's better to leave it alone. let the buyer do that if they please.
Please Do NOT buy replacement labels that do not have any markings they are reproductions. Even though you have no plans on selling a game now, in the future this will piss someone off once they find out it's fake. Also YOU might tell that buyer its fake, don't mean he will do the same.