I suppose it could if they knew you did it.
I have seen PCs that come from a shop with tape on that states "warranty void if removed".
If you don't mess the screw heads up on a laptop (and there is no seal), then I doubt there is proof you've been inside.
I suppose that sounds a bit dishonest, but you have to ask why some laptops makers sell 'genuine replacements'.
I'm sure they would like to charge to fit it to save some people messing them up, but if you feel competent enough to do it, then I would.