Does Restoring an Item Ruin its Value?

So I gather it would be in my best interest as to leave my Talk N Action Gordon's plastic in the way it is, but fix up the lining so it at least looks good, it doesn't need any new stickers which is a bonus, as for selling the items I'd be doing it for cheap regardless depending on the item so I'm not too bothered if the value is decimated on them, more on the items I own is my concerns

@LeyLandVictory2 So if I had a plarail Edward that was very beaten up, yellow in the face and damaged running board (in terms of paint) and I restored it, it would be worth less than what it would be priced if it was a brand new item but worth more than it was when it was ruined? Is that right?